Physics Dot Points Prelim Free Essays

string(165) " and outline how this may result in the bending of a wavefront Refraction is the phenomenon where waves appear to bend as the waves pass from one medium to another\." Physics syllabus dot point summary Nathan Kulmar 8. 2. 1. We will write a custom essay sample on Physics Dot Points Prelim or any similar topic only for you Order Now 1 describe the energy transformations required in one of the following: – mobile telephone – fax/modem – radio and television Energy is stored as chemical energy in the phone’s battery. Chemical energy is transformed into electrical energy to operate the phone. The microphone converts sound energy in to electrical energy. Antanna converts electrical to electromagnetic energy to send a siginal. The receiver speaker converts electric energy in to sound energy. 8. 2. 1. 2 describe waves as a transfer of energy disturbance that may occur in one, two or three dimensions, depending on the nature of the wave and the medium The energy from waves may spread out as a disturbance in Dimension- Energy travels in a straight line from the source 2 Dimensions- Energy spreads out in a plane or surface 3 Dimensions- Energy spreads out in to space surrounding the source in all directions 8. 2. 1. 3 identify that mechanical waves require a medium for propagation while electromagnetic waves do not Mechanical waves: require a medium, solid, liquid or gas to transfer energy. Electromagnetic waves: which don’t require a medium for transfer of energy. 8. 2. 1. define and apply the following terms to the wave model: medium, displacement, amplitude, period, compression, rarefaction, crest, trough, transverse waves, longitudinal waves, frequency, wavelength, velocity Medium: is what isn’t need for the electromagnetic spectrum to travel. Displacement: the distance from the point of equilibrium to the wave Amplitude: the distance to the point of maximum displacement Period: time taken o complete a single wave length Compression: an area where partials are pushed together Rarefaction: point where a partial reaches it’s maximum displacement vertically down Crest: the point where a partial reaches it’s maximum displacement vertically up Trough: the point where a partial reaches it’s maximum displacement vertically down Transverse waves: the direction of travel is at right angles to the oscillation (figure 2) Longitudinal waves: the direction of travel is parallel to the oscillation (figure 1) Frequency: the number of oscillations that pass a point in a second. V. remoteMissilesNight visibility gogglesSoft tissue treatment| Microwaves| Antenna| MobilesSending info. Cooking| Radio waves| Antenna| CommunicationAstronomy| 8. 2. 3. 4 explain that the relationship between the intensity of electromagnetic radiation and distance from a source is an example of the inverse square law I? 1d2 The intensity of the electromagnetic radiation is proportional to 1 divided by the distance squared. As the waves travel further from the point of origin they spread out and become less intense. I=k/d2 I=intensity k=constant d= distance 8. 2. 3. outline how the modulation of amplitude or frequency of visible light, microwaves and/or radio waves can be used to transmit information Information is converted into a wave and then placed on a carrier wave. It uses the properties of superposition to place the wave on to the carrier wave. Digital is made up of a series of one’s and zero’s. Digital encoding is made in to binary and are transmitted via light, microwaves, television waves and waves from the electromagnetic spectrum. There are two types of analogue transition one is AM. AM stands for Amplitude Modulation. This works by a using a high frequency carrier wave which has the modulation signal placed on it. Frequency will remain the same but amplitude will change. The other Form is FM. This stands for Frequency Modulation. A wave is frequency is chosen as the carrier wave and the modulation signal is placed on the carrier wave. Amplitude stays the same. 8. 2. 3. 6 discuss problems produced by the limited range of the electromagnetic spectrum available for communication purposes All EMR (electromagnetic radiation) will suffer attenuation (reduction in intensity) as they pass through the atmosphere or any other material. As the earth is bombarded with UV radiation from the sun the ionosphere becomes charged. This can cause problems such as ghosting which is a double image on your T. V. screen. Also large portions of EMR are unable to be used because they are too dangerous such as Gamma-rays and X-rays. Ultraviolet and visible are too difficult to produce and encounter too much interference. Near infrared and infrared also have difficult because of impurities in optical fibbers will absorbed the light. Microwaves and T. V. waves require line of sight to be practical. . 2. 4. 1 describe and apply the law of reflection and explain the effect of reflection from a plane surface on waves Electromagnetic waves may be reflected from a plane surface and they must obey the Law of Reflection: Angle of incidence equals the angle of reflection Incident ray, reflected ray and normal must all be in the same plane. 8. 2. 4. 2 describe ways in which applications of reflection of light, radio waves and microwaves have assisted in information transfer Light is used in optical fibbers to transmit data. The light is reflected off the inside of the glass tube and can carry multiple messages at the same time in a single fibber. Radio waves are reflected off the ionosphere to that they can travel a longer distance. Microwaves send transitions to satellites where they are reflected back through the atmosphere to earth. 8. 2. 4. 3 describe one application of reflection Plane surfaces Mirrors. They allow people to look at their bodies without distortion. Concave surfaces Satellite dishes. They focus incoming rays to a single point called the focus and energised the signal at this point. Convex surface Rear vision mirrors. They allow a large field of view in a small area but will give the viewer a false scene of distance Radio waves being reflected by the ionosphere Radio waves are reflected off the ionosphere to provide a greater distance to which a listener can be from the source of the broadcast. 8. 2. 4. 4 explain that refraction is related to the velocities of a wave in different media and outline how this may result in the bending of a wavefront Refraction is the phenomenon where waves appear to bend as the waves pass from one medium to another. You read "Physics Dot Points Prelim" in category "Papers" If wavefronts strike a boundary at any other angle other than 90 ° than a change of speed will occur. If a wave goes from one medium to another and the speed is lower than it will bend towards the normal. If it goes into a medium where the speed is faster than it will bend away from the normal. The waves bend because the incident ray first strikes the medium it slows down and the rest of the ray continues at the same speed until it makes contact with the medium. It is the wavelength that changes not the frequency. 8. 2. 4. 5 define refractive index in terms of changes in the velocity of a wave in passing from one medium to another The refractive index is the ratio of the two wave velocities during the efraction. The refractive index is a measure of how much the light bends. 8. 2. 4. 6 define Snell’s Law: V1V2=sin isin r V1 and V2 are the speeds of the waves in wave in the different mediums. Sin i is the angle of incidence and sin r is the angle of reflection. It is the relationship between speed, wavelength and angles of incidence refraction was determined experimentally by Wi llebrorod Snell and is known as Snell’s law. 8. 2. 4. 7 identify the conditions necessary for total internal reflection with reference to the critical angle If the critical angle is reached than the angle or reflection is 90 °. When the critical angle is exceeded than the light can’t escape and total internal refraction occurs. The light must be travelling from a medium with a higher refractive index to one with a lower refractive index. 8. 2. 4. 8 outline how total internal reflection is used in optical fibres Optical fibres are one application of total internal refraction. They are made of high purity glass, the central region is called the core and the outer region called the cladding. The cladding confines the light to the core and thus must have a lower refractive index than the core. Once information is digitally encoded, at the transmitting end, the signal is converted from electrical energy to light energy and then transmitted along the optical fibre. The information is sent as a series of coded pulses of light. The pulse is either on or off. At the receiving end it is decoded. 8. 2. 5. 1 identify types of communication data that are stored or transmitted in digital form CD ROMs (Compact Disk Read-Only Memory) these discs store data in digitised form as tiny bits. They are read using a low power laser beam. They cannot be edited and are read only. They are fairly slow to read and can only store 8000Mbytes DVD (Digital Versatile Discs) these disks can hole 5 billion bytes of data, thus making possible the storage of memory consuming movie length video and sound. GPS (Global Positioning Systems) this worldwide system uses a fleet of 24 satellites that transmit signals constantly. A GPS system, few hundred dollars, can interact with the satellite to pinpoint your latitude, longitude and altitude with in 50m. 8. 3. 1. 1 discuss how the main sources of domestic energy have changed over time. The sources of domestic energy have changed rapidly over time: * 50,000 BC: control of fire: cooking and heating * 10,000 BC: domestication of animals: animal power for transport and ploughing. * 3,000 BC: wind and water power: sailing boats and windmills * 1750 AD: burning of coal begins to replace wood. Steam engines, trains, steam, ships. * 1780-1800: scientific investigations of the properties of electricity. Conflicting theories, scientific curiosity small amounts of energy in batteries. * 1830’s: discover how to generate electricity using a â€Å"dynamo† (generator). Still used in scientific labs. * 1880-1910: a flood of inventions such as the light bulb, telephone, gramophone and radio were create with electricity. * 1950- : all industrialized nations had become totally converted to electricity for domestic power. 8. 3. 1. 2 assess some of the impacts of changes in, and increased access to, sources of energy for a community Some impacts of charges in sources of energy are: * The use of coal has had a particularly large impact on our society. * Coal burns hot fires to make steel and other metals. Steel major factor that lead to the industrial revolution. * Coal lead to the development of the steam engine. * Pollution and global warming was created. 8. 3. 1. 3 discuss some of the ways in which electricity can be provided in remote locations Use small generators that rotate a coil by a petrol or oil motor. Solar cells and wind generators are also used to convert sunlight and wind into electricity. 8. 3. 2. 1 describe the behaviour of electrostatic charges and the properties of the fields associated with them * Two types of charges positive and negative Charges go away from positive, charges go towards negative * An electrostatic charge is a charge due to an excess or deficiency of electrons. * A body with equal number of protons and electrons will be neutral. * Body has an excess of electron is negatively charged. 8. 3. 2. 2 define the unit of electric charge as the coulomb Electric charge is measured in coulombs the coulomb (c) is the SI unit of electric charge. 1 coulomb = 1c = 6. 25 x10^18 charge = 1. 6 x10^19 charge 8. 3. 2. 3 define the electric field as a field of force with a field strength equal to the force per unit charge at that point: E=Fq E = magnitude of electric field (NC-1) Newton per coulomb q = charge (C) coulombs F = force (N) Newton 8. 3. 2. 4 define electric current as the rate at which charge flows (coulombs/ second or amperes) under the influence of an electric field Current is the rate at which charge flows (Csec. or Amperes) under the influence of an electric field. I= QT I = current Q= charge (coulombs) T= time (sec) 8. 3. 2. 5 identify that current can be either direct with the net flow of charge carriers moving in one direction or alternating with the charge carriers moving backwards and forwards periodically DC = direct current Charge moves in one direction Direct positive to negative movement AC = alternating current Charge moves back and forth periodically. Directions changes 50 times per second. 8. 3. 2. 6 describe electric potential difference (voltage) between two points as the change in potential energy per unit charge moving from one point to the other (joules/coulomb or volts) Electric potential difference (Voltage) between two points is the change in potential energy per unit charge moving from one point to another (joules/coulomb or Volts). . 3. 2. 7 discuss how potential difference changes between different points around a DC circuit Potential difference can vary at different points around a circuit for example there will be different voltage drops across various resistors, light globes and rheostats which would be different to the voltage rise across the power pack. 8. 3. 2. 8 identify the difference between conductors and insulators Insulators will not allow electricity to flow through them bec ause they have a very high resistance. Conductors have a very low resistance and therefore will allow current to flow through them. 8. 3. 2. 9 define resistance as the ratio of voltage to current for a particular conductor: V=IR V= Voltage I= Current in amps R= Resistance in ohms 8. 3. 2. 10 describe qualitatively how each of the following affects the movement of electricity through a conductor: Length: Resistance is proportional to length; the longer a conductor the greater the resistance Cross sectional area: larger the cross-section the lower the resistance. Temperature: temperature increases ions vibrate increasing resistance. Material: material of a conductor influences resistance; copper is commonly used for household wiring, gold or silver used when minimal resistance required. 8. 3. 3. 1 identify the difference between series and parallel circuits Series: * There is only one current pathway. * Current is the same throughout the whole circuit * If a series circuit is broken at any point then the electricity cannot flow through it. * Current remains constant and voltage varies (VT=V1+V2+V3). Parallel: * There is more then one current pathway. * All components have the same potential difference across them * In parallel, voltage remains constant and current varies (IT=I1+I2+I3). 8. 3. 3. 2 compare parallel and series circuits in terms of voltage across components and current through them Parallel| Series| VT= V1 = V2 = V3| VT= V1 + V2 + V3| IT=I1 + I2 + I3| IT=I1 = I2 = I3| 8. 3. 3. 3 identify uses of ammeters and voltmeters Ammeters measure the flow of electrons through a point in the circuit. Voltmeters measure the potential difference between two points. 8. 3. 3. 4 explain why ammeters and voltmeters are connected differently in a circuit Ammeter: cannot change the current being measured, must have minimum resistance, current must flow through the ammeter, MUST BE PLACED IN SERIES Voltmeter: measure the penitential difference (voltage) between two points in a circuit, PLACED IN PARALLEL CURCUITS, important that voltmeter has high resistance so that there is not affect on the circuit. 8. 3. 3. explain why there are different circuits for lighting, heating and other appliances in a house In a house there are separate circuits for lighting, heating and other appliances so that appliances that require large amounts of current can still function without over-loading the circuit. If everything was on one circuit there would be too much current used and the wires would become hot and potentially cause a fire. 8. 3. 4. 1 explain that power is the rate at which energy is transfor med from one form to another Power is defined as the rate at which energy is transformed from one form to another. watt=1 W=1J/s 1kW=1000watts P=ET Power ((Joules = watts (W)) = Energy (J) / time (s) 8. 3. 4. 2 identify the relationship between power, potential difference and current Power is the number of joules per second (watts), for every current (I in Amps), Voltage (v in volts) are dissipated. P=VI Power (Watts) = Voltage (V) x Current (A) 8. 3. 4. 3 identify that the total amount of energy used depends on the length of time the current is flowing and can be calculated using: Energy=VIt Electrical energy (joules) = Voltage (volts) x Current (amps) x Time (sec) P=VI Power (Watts) = Voltage (V) x Current (A) P=ET Power ((Joules = watts (W)) = Energy (J) / time (s) 8. 3. 4. 4 explain why the kilowatt-hour is used to measure electrical energy consumption rather than the joule 1kW. h is the energy used by a 1 kW appliance operating for 1 hour. Measuring in joule is a big inconvenient because 1 joule is a very tiny amount of energy. 8. 3. 5. 1 describe the behaviour of the magnetic poles of bar magnets when they are brought close together Magnets have 2 different poles north and south. They can either be attract or repel each other. Opposite poles attract, same poles repel. 8. 3. 5. 2 define the direction of the magnetic field at a point as the direction of force on a very small north magnetic pole when placed at that point The direction of a magnetic field is the direction of force on a very small magnetic north pole placed in the field. The currents from the north pole more towards to the south pole. 8. 3. 5. 3 describe the magnetic field around pairs of magnetic poles Field lines come out of the North and into the south. Field lines never cross. The magnitude of the field is indicated by the density of the field lines. . 3. 5. 4 describe the production of a magnetic field by an electric current in a straight current-carrying conductor and describe how the right hand grip rule can determine the direction of current and field lines The direction of the magnetic field is described by the right hand rule. Right hand grip rule: Grip wire with right hand, thumb pointing in direction of conventional current, fingers will curl around in the direction of the magnetic field. 8. 3. 5. 5 compare the nature and generation of magnetic fields by solenoids and a bar magnet * A solenoid is a coil of wire. When a current flows in the solenoid it produces a magnetic field around the coil which is similar to that of a bar magnet. * In a solenoid the field continues through the middle as parallel lines. * The direction of the magnetic field inside a solenoid is given by the right hand rule. 8. 3. 6. 1 discuss the dangers of an electric shock from both a 240 volt AC mains supply and various DC voltages, from appliances, on the muscles of the body * The neuromuscular system runs on the movement of electrical changes. An electric current through the body has the effect to disrupt its normal function. A typical response of your body’s muscles to an electric shock would be: * Muscles contract so you won’t be able to let go. * Muscles controlling the diaphragm cause it to clamp (can’t breathe ) * Heart muscle goes into fibrillation (stops effective beating till heart stops altogether) * Death * Human bodies can withstand ten times as much DC current as AC, AC operates on frequency (50-60 Hz) which is the same frequency our heart operates making AC significantly more lethal than DC. 50-100 mA are the lethal limits for electric shock. 8. 3. 6. describe the functions of circuit breakers, fuses, earthing, double insulation and other safety devices in the home Circuit breakers: they use an electromagnet to mechanically break the circuit. Once the current exceeds the maximum value. Fuses: they prevent overloading of circuits. They are made of a metal with a low melting point. They melt when the current through the circuit exceeds the wiring. They are usually contained in high melting point materials to avoid fires. Earthing: they protect from shock. If an appliance has any metal exposes than it will have the outer cover earthed to protect shock. It works on the bases that there is less resistance through the wire rather than through a person. Double insulation: house hold wiring must be covered by an insulator. Usually made of plastic ((polyvinylchloride, (PVC)) many have double insulating in case the inner insulation melts when the metal gets to hot. 8. 4. 1. 1 identify that a typical journey involves speed changes In a typical car journey, a car may travel at different speeds, accelerate and decelerate, changes direction and stops therefore although there is an average speed for the entire journey, the vehicle does not travel at a constant speed. . 4. 1. 2 distinguish between scalar and vector quantities in equations Scalar quantities are those that specify size (magnitude), but not direction. Vector quantities are defined by both size (magnitude) and direction. Vectors| Scalar| Force| Mass| Velocity| Speed| Displacement| Distance| Acceleration| Work| Momentum| Energy| Magnetic Fields| Power| Electric Fields| Time| 8. 4. 1 . 3 compare instantaneous and average speed with instantaneous and average velocity Average Speed = Distance/Total Time Instantaneous Speed is the speed of an object at a particular instant of time. Velocity (v) is the time rate of change of the displacement. It is a vector; it requires both size and direction. It is speed with a direction. Displacement (s) is distance in a given direction. Instantaneous velocity is the velocity at a particular instant, the speed and the direction. Average Velocity is displacement/time. 8. 4. 1. 4 define average velocity as: vav= ? r? t r = s = displacement. Average velocity= change in displacement/ change in time. 8. 4. 2. 1 describe the motion of one body relative to another Motion occurs when an object changes its position relative to other or some co-ordinate system (a frame of reference). If a change in direction occurs thorough vector qualities, must be dealt with as vectors. 8. 4. 2. 2 identify the usefulness of using vector diagrams to assist solving problems Vectors qualities have magnitude and direction. Adding Vectors Draw the first vector. Draw the second vector starting from the end of the first. The resultant vector is the line joining the beginning of the first vector to the end of the second. 6km 8km 10km a 6km 8km 10km a Subtracting Vectors V1 – V2 = Change in VChange V = V (f) – V (i) V1 -V2 V1 – V2 V1 -V2 V1 – V2 Change = Final – Initial Change V 8-(-10) = 18 -10m/s 8m/s -10m/s m/s 8. 4. 2. 3 explain the need for a net external force to act in order to change the velocity of an object Forces can internal or external to a system but only the external forces can affect the motion of the system. Net force = sum of all forces. Change in velocity the object must accelerate. An object will remain in constant motion (rest or 0 velocity) unless an unbalanced force acts on the object. To accelerate there must be an outside force acting (Newton’s 1st law). Newton’s first law states that: A body continues in its state of rest or uniform velocity unless acted upon by an unbalanced force. . 4. 2. 4 describe the actions that must be taken for a vehicle to change direction, speed up and slow down Acceleration is defined as the time rate of change of velocity. Acceleration refers to: Speeding Up: this can be done by using the accelerator Slowing Down: this can be done by using the cars brakes Changing Direction: Using the steering wheel 8. 4. 2. 5 describe the typical effects of external forces on bodies including: Friction between surfaces Air resistance There are a number of external forces working on a car and these include: Friction with the Road Air Resistance The weight of the car Friction is a force that we encounter everyday in everything we do. Friction is a force that always opposes motion. Friction arises when two different materials are in contact with each other. The tires make contact with the road surface and as a result there is friction. This means that the vehicle has traction and does not simply slide. Air Resistance is a form of Friction. As a vehicle moves through the air the two materials, the vehicles body and the air, move past each other. Air resistance limits the speed of the vehicle but it can be minimized by designing a vehicle so that it is aerodynamically shaped. . 4. 2. 6 define average acceleration as: vav= ? r? t therefore vav=v-ut Acceleration is a change in velocity over a certain time period. It can be positive or negative. v= final velocity, u= initial velocity, t= time taken 8. 4. 2. 7 define the terms ‘mass’ and ‘weight’ with reference to the effects of gravity Mass: Is the measure of the amount of mat ter in an object Measure of inertia (resistance to acceleration) Independent or the effects of gravity Measured in grams. Weight Is the force of gravity on an object. On earth weight is the mass x 9. 8 Dependent on the amount of mass Measure of the gravity and force on an object Measured in Newton’s. 8. 4. 2. 8 outline the forces involved in causing a change in the velocity of a vehicle when: Coasting with no pressure on the accelerator Friction with the Road Air Resistance Force Pushing car along Pressing on the accelerator The driver is supplying more fuel to the engine. This allows the engine to apply a greater force on the wheels and hence make the car speed up. Velocity and acceleration acting in the same direction. Pressing on the brakes Increasing the friction between the brake pads and the metal discs making it harder for the wheels to turn. Velocity and Acceleration acting in different directions. Passing over an icy patch on the road There is less friction and the wheels can’t get as much grip so they may slide. The car will move at a constant velocity until acted upon by an external force. Climbing and descending hills Friction Air Resistance The cars weight causes it to slow down when going up the hill and speed up when going down the hill Following a curve in the road Centripetal force is causing the car to accelerate as the velocity is changing owing to the change in direction. 8. 4. 2. interpret Newton’s Second Law of Motion and relate it to the equation: F=ma F= Force in Newtons m= mass a= acceleration 8. 4. 2. 10 identify the net force in a wide variety of situations involving modes of transport and explain the consequences of the application of that net force in terms of Newton’s Second Law of Motion The acceleration of an object is proportional to the unbalanced force acting on it and is i nversely proportional to the mass. The consequences of net external force acting on a model of transport are acceleration, deceleration and a change of direction in motion. Centripetal force (circular motion) The force causing the turning is always towards the centre of the circle. Force (centripetal) = mv^2/ R R=radius, V= instantaneous velocity, M= mass 8. 4. 3. 1 identify that a moving object possesses kinetic energy and that work done on that object can increase that energy Kinetic Energy is the energy an object possesses because it is moving. Kinetic energy is dependent on the mass and the square of the velocity of the body as indicated by: KE=12mv2 E= kinetic energy (joules) M=mass of the object (kg) V=velocity (m/s) Work (W) is done when a force (F) is moved through a distance (s). Work is the product of a force and the distance moved in the direction of that force. W=Fs. Work transfers energy through the motion of a force. When work is done, energy is required. W = Change in Kinetic energy 8. 4. 3. 2 describe the energy transformations that occur in collisions In collisions objects exert forces on each other. Collisions can be either: Elastic Non-Elastic Elastic Collisions If in a collision, kinetic energy is conserved, the collision is said to be elastic. An example would be when Gas molecules collide with each other and with the walls of their container as kinetic energy is not decreased. Inelastic Collisions In inelastic collisions, kinetic energy is not conserved. Some of the Kinetic energy is transformed into other forms of energy such as heat and sound. If the colliding parts stick together, the collision is inelastic 8. 4. 3. 3 define the law of conservation of energy In all types of interactions, both elastic and inelastic, total energy is conserved. Energy cannot be destroyed only can be changed from one form to another. . 4. 4. 1 define momentum as: p=mv Momentum= mass (kg) x velocity (m/s) Unit of momentum= kilogram-meter/sec To stop a moving object, forces must be applied and the forces relate to two factors, the mass of the object and the velocity of the object. The time rate of change of momentum is proportional to the resultant force and acts in the direction of the force. Always conserved Vector quantity 8. 4. 4. 2 defi ne impulse as the product of force and time Impulse = F (force) x t (time) Impulse = change in momentum Impulse = Ft = mv – mu mv = final momentum u = initial momentum The unit of Impulse is N. s which is the same as the Unit of momentum= kilogram-meter/sec (kg. m/sec) 8. 4. 4. 3 explain why momentum is conserved in collisions in terms of Newton’s Third Law of motion Force (action) = Force (reaction) Conservation of Momentum The total momentum of a system is always the same unless the system on by some external force. P (before) = P (after) m1u1+m2u2= m1v1+m2v2 This equation shows that: the vector sum of the momentum of the objects before collision equals the vector sum of the momentum after collision. Momentum is conserved only in isolated systems (those free from external forces). The Law of the Conservation of Momentum can be stated as: In interactions between objects, momentum is conserved in an isolated system. 8. 4. 5. 1 define the inertia of a vehicle as its tendency to remain in uniform motion or at rest Newton’s 1st law: Inertia: â€Å"Tendency of any object to resist any change in motion. † E. g. when a car stops suddenly, the objects and people in the car remain in the current motion unless acted upon by an external force such as a seatbelt. 8. 4. 5. discuss reasons why Newton’s First Law of Motion is not apparent in many real world situations Common experience is not apparent in Real World Situations as the driver of a car still needs to depress the accelerator to move at a constant rate because of friction between the car and the road. 8. 4. 5. 3 assess the reasons for the introduction of low speed zones in built-up areas and the addition of air ba gs and crumple zones to vehicles with respect to the concepts of impulse and momentum Introduced low speed zones into built areas to reduce the speed of drivers as the faster you are moving the more damage you do in a collision. Crumple Zones were introduced so that the front and rear end of the car should crumple in a collision which increases the time it takes for the car to come to rest so the forces are lessened. Air Bags were introduced which provide a cushion and takes the impact out of a collision. 8. 4. 5. 4 evaluate the effectiveness of some safety features of motor vehicles Seat Belts They are effective in limiting the effect of inertia when a vehicle breaks suddenly. It absorbs a lot of the force of a collision. Airbags Air Bags were introduced which provide a cushion and takes the impact out of a collision. Crumple Zones Crumple Zones were introduced so that the front and rear end of the car should crumple in a collision which increases the time it takes for the car to come to rest so the forces are lessened. 8. 5. 1. 1 outline the historical development of models of the Universe from the time of Aristotle to the time of Newton Plato| planets move in spherical orbits around the earth (geocentric) | Eudoxus| maintained Plato’s concepts of spherical motions, complex arrangements of circular motions| Aristotle| developed Eudoxus model to 53 spheres. | Aristarchus| The sun is in the centre (heliocentric) with everything orbiting around it and epicycle moments to explain planetary movements; Earth must rotate on its axis, so it appears that everything moves around us. | Ptolemy| believed in geocentric universe, stars existed on a sphere which rotated every 24 hours, earth is a sphere and at rest, motion of sun and plants moved in perfect circles. | Copernicus| heliocentric universe, sun was the centre and planets orbited the sun in fixed circular motions, earth traveled around the sun in 1 year and spins on its axis every 24 hours. Galileo| first to use a telescope, supported the heliocentric idea of Copernicus, worked on gravitational theory disproved Aristotle concepts of the motion. | Sir Isaac Newton| from work on motion realized that a forcer must be acting on an object such as the moon, law of universal gravitation, this explain where things stayed in orbit, since the time of Newton the heliocentric model was accepted. | 8. 5. 2. 1 outline the discovery of the expansion of the Universe by Hubble, following its earlier prediction by Friedmann Alexander Friedman predicted that the universe was expanding. The predictions rose from calculations based on Einstein’s, general theory of relativity. Edwin Hubble designed a new and a bigger telescope that leads to the discovery of the red shift proving that the universe is expanding. A red shift corresponds to a shift to the lower frequency (longer wavelength). This indicates that the light source, the galaxy is moving away from us. All galaxies show this effect indicating that the universe is expanding. 8. 5. 2. 2 describe the transformation of radiation into matter which followed the ‘Big Bang’ After the temperature had dropped enough. The energy began to be converted in to matter. Hydrogen atoms formed from protons and electrons. 8. 5. 2. 3 identify that Einstein described the equivalence of energy and mass E=mc2 E= energy (Joules) m= mass (kg) c= speed of light (3 x 108 ms-1) 8. 5. 2. 4 outline how the accretion of galaxies and stars occurred through: Expansion and cooling of the Universe The cooling of the universe allowed the formation of matter. This began to overwhelm the radiation Subsequent loss of particle kinetic energy As the temperature fell this resulted in a loss of kinetic energy (as temperature is the measure of average kinetic energy of the particles) Gravitational attraction between particles Loss in Kinetic energy meant that the increased gravitational force between particles took effect Lumpiness of the gas cloud that then allows gravitational collapse The greater density of areas of the gas clouds allowed gravity to begin 8. 5. 3. 1 define the relationship between the temperature of a body and the dominant wavelength of the radiation emitted from that body The hotter the star the shorter the wave length. Hot star: short wave length, more energy. Cold star: long wave length, less energy 8. 5. 3. 2 identify that the surface temperature of a star is related to its colour Red | Long wavelength| Orange| | Yellow | | White blue- white| Short wavelength| The hotter the star gets the more it will shift towards the blue end of the spectrum and thus the shorter the wavelength. 8. 5. 3. 3 describe a Hertzsprung-Russell diagram as the graph of a star’s luminosity against its colour or surface temperature In the Hertzsprung-Russell diagram a stars surface temperature and luminosity (brightness) are plotted against each other. This is because there is a relationship between the two. 8. 5. 3. 4 identify energy sources characteristic of each star group, including Main Sequence, red giants, and white dwarfs Star group| Fuel| Characteristics| Main sequence| H then He| They are from the top left of the Hertzsprung-Russell diagram to the bottom right. This shows a trend of hot and bright to cold and dull| Red giants| H then He| In the upper right corner of the Hertzsprung-Russell diagram and are bright but cold| White dwarfs| C and O ions| Bottom left of the Hertzsprung-Russell diagram. They are very hot but dim and small. 8. 5. 4. 1 identify that energy may be released from the nuclei of atoms Light atoms like H will fuse together at extreme temperatures to for stable atoms. This produces energy. Uranium on the other hand has very unstable nuclei and will break down by emitting energy or partials randomly. That may be in the form of ? , ? or gamma rays. 8. 5. 4. 2 describe the nature of emissions from the nucle i of atoms as radiation of alpha ? and beta ? particles and gamma ? rays in terms of: ionising power penetrating power effect of magnetic field effect of electric field Radiation| Ionizing power| Penetrating Power| Effect of Magnetic Field| Effect of Electric Field| Alpha Particle| Very high Strong| Low a few cm in the air| Affected according to right hand palm rule| Limited – very small| Beta Particle| Less than AlphaWeak| Higher than Alpha thin sheets of lead| Large| Large| Gamma Ray| Less than BetaVery Weak| Very High Several cm of lead| Zero| Zero| 8. 5. 4. 3 identify the nature of emissions reaching the Earth from the Sun Solar wind consists of a stream of ionised particles, mostly protons and electrons that flow from the sun in all directions at speeds of about 400 km. -1. The source of the wind is the sun’s hot corona – the outer atmosphere of the sun extending a distance of a few solar radii into space. Most of the corona consists of vast arches of hot gas – solar flares – that are millions of kilometres in length and are caused by the sun’s magnetic field. The Solar wind comes from regions called co ronal holes, regions of cooler, less dense gas. As the sun rotates there is a periodic variation in Solar wind activity every 27 days. The Solar wind is responsible for pushing the tail of comets away from the sun. 8. 5. 4. 4 describe the particulate nature of solar wind Sunspot cycle is a pattern of increasing and decreasing sunspots. Sun spots are a dark spot on the sun with lower temperatures and intense magnetic activity. Cycle is between 7-13 years. Two types of emission reaching Earth from the sun: electromagnetic radiation and solar winds. Earth’s atmosphere and magnetic field shelters as from theses emissions. The sunspots themselves last for several days although larger ones may last up to a few weeks. The number of particles and their velocity increases following sunspot activity and solar flares meaning that the solar wind is greater in the time of maximum sunspots. . 5. 4. 5 describe sunspots as representing regions of strong magnetic activity and lower temperature Sunspots are relatively cool areas (~4500K), with magnetic field strengths some thousands of times stronger than the Earth’s magnetic field, that appear as dark imperfections in the photosphere. They result from the penetration of magnetic field lines through the photosphere and are ~8000km across. Except for the smaller ones, all sunspots have a dark inner region – the umbra – where the magnetic field is strongest surrounded by a less dark region – the penumbra – where the magnetic field is weakest. How to cite Physics Dot Points Prelim, Papers