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P2 Physics Additional Science Key Recall Questions *Cover up the answers, ask yourself a question (or get your partner to ask you), if you get it right then tick the chart, wrong put a cross. Keep practising until all columns are ticked! P2.1 Forces and their effects_1 Key Recall Question 1. How are forces represented? 2. What is a resultant force? 3. What will happen if the resultant force acting on a stationary object is zero? 4. What will happen if the resultant force acting on a stationary object is not zero? 5. What will happen if the resultant force acting on a moving object is zero? 6. What will happen if the resultant force acting on a moving object is not zero? 7. What is the unit for force? 8. How are force, mass and acceleration linked? 9. What are the units of mass? 10. What is the unit of acceleration? Answer By an arrow, ideally from where the force originates A single force which replaces a number of forces all acting at a particular point. The resultant force has the same effect on the motion as all the forces acting together. The object will stay stationary. The object will accelerate in the direction of the resultant force. The object will move at the same speed and in the same direction. The object will accelerate in the direction of the resultant force. Newtons (N) Force = mass x acceleration F(N) = m (kg) x (m/s2) Kilograms (kg), grams (g) or sometimes tonnes (1000kg) Metres per second squared (m/s2) Question Date: Date: Date: Date: Date: Date: Date: Date: Date: Date: Date: Date: Date: 1 2 3 4 5 6 7 8 9 10 P2.1 Forces and their effects_2 Key Recall Question 1. What does the gradient of a distance-time graph represent? 2. What are the units of speed (velocity)? 3. What does a horizontal line on a distance-time graph represent? 4. How do you calculate the speed (velocity) from a distance-time graph? 5. What is the difference between speed and velocity? 6. What does the gradient of a velocity-time graph represent? 7. What are the units for acceleration? 8. What does a horizontal line on a velocity-time graph represent? 9. How do you calculate the acceleration from a velocity-time graph? 10. How do you calculate the distance from a velocity-time graph? Answer Constant speed (velocity) Metres per second (m/s) or kilometres per hour (km/hr). NOTE; miles per hour is not an SI unit. The object is stationary. Speed (velocity) is distance/time so use the axis to find the distance travelled and divide it by the time taken. The velocity of an object is its speed in a given direction. Acceleration. metres per second squared (m/s2) The object is moving at a constant velocity. Use a = v-u t Where a = acceleration (m/s2), v = final velocity (m/s), u = initial velocity (m/s) and t = time (s) Work out the area underneath the graph. The answer will be in metres (m). Question Date: Date: Date: Date: Date: Date: Date: Date: Date: Date: Date: Date: Date: 1 2 3 4 5 6 7 8 9 10 P2.1 Forces and their effects_3 Key Recall Question 1. What happens to the forces when a vehicle travels at a steady speed? 2. Which force are most of the resistive forces acting on a vehicle caused by? 3. How is the braking force affected by speed? 4. What is ‘stopping distance’? 5. What three things can a driver’s reaction time be affected by? 6. What happens to the temperature of the brakes when you apply them and why? 7. What can braking distance be affected by? 8. If an object moves through a fluid (liquid or gas) faster, what happens to the frictional force? 9. Why does a falling object initially accelerate? 10. What will eventually happen to the resultant force of a falling object? 11. What is ‘terminal velocity’? Answer The resistive forces balance the driving force Air resistance. The bigger the speed the greater the braking force required to stop it in a certain distance. The distance the driver travels during the driver’s reaction time (thinking distance) and the distance it travels under the braking force (braking distance). Tiredness, drugs and alcohol. It increases because the work done by the friction force between the brakes and the wheel reduces the kinetic energy of the vehicle so the temperature of the brakes increases. Poor weather (icy and wet conditions) and poor condition of the vehicle (tyres or brakes). It will increase Due to the force of gravity It will be zero The speed (velocity) an object reaches when the resultant forces are zero. It is measured in m/s Question Date: Date: Date: Date: Date: Date: Date: Date: Date: Date: Date: Date: Date: 1 2 3 4 5 6 7 8 9 10 11 P2.1 Forces and their effects_4 Key Recall Question 1. How do you calculate the weight of an object? 2. What will happen to a spring when a force is applied? 3. What type of energy is stored in a spring when it is stretched? 4. What is the extension for an elastic object directionally proportional to? 5. What is the limit of proportionality? 6. In F = k x e, what does e represent? 7. In F = k x e, what does k represent? 8. What are the units for ‘spring constant’? 9. If a spring has a spring constant of 3 and it is extended by 0.1 m, what is the Force applied to produced this extension? Answer Mass(kg) x gravity (N/kg) = Weight (N) It will change shape and stretch Elastic potential energy The force applied The point at which the force applied and extension is no longer proportional The extension in metres. The spring constant Newtons per metre (N/m) F=k x e F = 3 x 0.1 F = 0.3 N Question Date: Date: Date: Date: Date: Date: Date: Date: Date: Date: Date: Date: Date: 1 2 3 4 5 6 7 8 9 P2.2 The kinetic energy of objects speeding up or slowing down_1 Key Recall Question 1. What is ‘work done’? 2. What is the unit for work done? 3. What is transferred when work is done on an object? 4. Will the amount of work done to move an object across ice be smaller or greater than to move the same object, the same distance across grass? 5. What is ‘Power’ and what are its units? 6. What is gravitational potential energy? 7. What are the units for gravitational field strength (g)? 8. If the gravitational field strength on Earth is 10 N/kg what is the weight of someone who has a mass of 70 kg? 9. If the person in question 8 stood on a stool which is 1m high, what would their gravitational potential energy be? Answer When a Force causes an object to move through a distance. W = F (N) x d (m) Joules (J) Energy It will be smaller because there are less frictional forces to counteract. The work done or energy transferred in a given time. P = E/t. The units for Power are Watts (W), Energy are joules (J) and time is seconds (s) The energy that an object has due to its position in a gravitational field. Ep = m x g x h Where Ep is the change in gravitational potential energy in joules (J), m is the mass in kilograms (kg), g is the gravitational field strength in newtons per kilogram (N/kg) and h is the change in height in metres (m) N/kg 70 kg x 10 N/kg = 700 N (weight = m x g) Ep = m x g x h Ep = 70 x 10 x 1 Ep = 70 J Question Date: Date: Date: Date: Date: Date: Date: Date: Date: Date: Date: Date: Date: 1 2 3 4 5 6 7 8 9 P2.2 The kinetic energy of objects speeding up or slowing down_2 Key Recall Question 1. What two factors does the kinetic energy of an object depend on? 2. How can the kinetic energy equation be rearranged to calculate speed? 3. What must an object be doing in order to have momentum? 4. What is the equation for calculating momentum? 5. How does the momentum of an object before a collision or explosion compare to the momentum after a collision (assuming it is a closed system)? 6. What are the units for momentum? 7. If an object has a momentum of 30 kg m/s and it collides into another object and sticks to it, what will the momentum of the two objects be? 8. The mass of the two objects in question 7 is 10 kg. What will the velocity of the objects be? 9. When a cannon is fired it often moves backwards. What is this backward movement called? 10. How can the momentum of the recoil of a gun be the same as the momentum of the bullet, but the person firing the gun is not injured? 11. If two ice skaters, of mass 60 kg and 90 kg, are standing in the middle of an ice rink and they push against each other, which ice skater will move with the greatest velocity? Answer Mass and speed. Ek = ½ x m x v2 V = 2 x Ek M Moving p=m x v p is momentum in kilogram metres per second (kg m/s), m is mass in kilograms (kg) and v is velocity in metres per second (m/s) It is equal kg m/s 30 kg m/s v = p/m, v = 30/10 so v = 3 m/s Recoil Because the mass of the bullet is much smaller than the mass of the gun. Therefore the velocity of the bullet can be much greater than the velocity of the gun, thus making the momentum of the two objects the same. The 60 kg ice skater because to equal the momentum of the other ice skater (p = m x v) they must have a greater velocity. Question Date: Date: Date: Date: Date: Date: Date: Date: Date: Date: Date: Date: Date: 1 2 3 4 5 6 7 8 9 10 11 P2.3 Currents in electrical circuits_1 Key Recall Question 1. What happens when insulating materials are rubbed against each other? 2. What particle is rubbed off between each insulating material when they are rubbed together? 3. How does one of the insulating materials become negatively charged? 4. How does one of the insulating materials become positively charged? 5. What happens if two electrically charged objects are brought together? 6. If two electrically charged materials, which carry the same charge, are brought near to each other what will happen? 7. If two electrically charged materials, which carry different charges, are brought near to each other what will happen? 8. What sort of materials can electrical charges move through easily? 9. What is electric current? 10. What does the size of electric current depend on? 11. How can the size of current be calculated? Answer They become electrically charged. Electrons (which have negative charges) It gains electrons (from the other insulating material) It loses electrons (to the other insulating material) They exert a force on each other (e.g. a charged balloon near to charged hair) They will repel each other. They will attract each other. Metals (think back to chemistry and their structure to understand why) The flow of electric charge. The rate of flow of electric charge. I = Q/t where I is current in amperes (A), Q is the charge in coulombs (C) and t is the time in seconds (s). Question Date: Date: Date: Date: Date: Date: Date: Date: Date: Date: Date: Date: Date: 1 2 3 4 5 6 7 8 9 10 11 P2.3 Currents in electrical circuits_2 Key Recall Question Answer 1. What is the potential difference (voltage) between two points in an electric circuit? 2. How can potential difference be calculated? 3. What do these circuit symbols represent? The work done (energy transferred) per coulomb of charge that passes between the points. V = W/Q where V is the potential difference in volts (V), W is the work done in joules (J) and Q is the charge in coulombds (C) Open switch, closed switch, lamp and fuse 4. What do these circuit symbols represent? Cell, battery, resistor and voltmeter 5. What do these circuit symbols represent? Ammeter, light dependent resistor (LDR), variable resistor and thermistor 6. What do these circuit symbols represent? Light emitting diode (LED), light dependent resistor (LDR) and diode. 7. What are current-potential difference graphs used for? 8. What does the current-potential difference graph for a resistor at constant temperature look like? 9. What is the current through a resistor (at a constant temperature) directly proportional to? They show how the current through a component varies with the potential difference across it. A straight diagonal line going through the point of origin. Potential difference across the resistor. Question Date: Date: Date: Date: Date: Date: Date: Date: Date: Date: Date: Date: Date: 1 2 3 4 5 6 7 8 9 P2.3 Currents in electrical circuits_3 Key Recall Question 1. How can the resistance of a component be found out? 2. How can current, potential difference and resistance be calculated? 3. If a component has a resistance of 10 and a current of 2 A is passing through it, what will be the potential difference? 4. If a component, which has a larger resistance than the component in question 3, is placed in the circuit, what will happen to the current? 5. How do you work out the potential difference of four 3 V cells connected in series? 6. If one of the cells in question 5 was connected a different way around, what would the potential difference be? 7. When three 2 resistors are place in series, how can you calculate the total resistance? 8. If a lamp, resistor and fuse (which all have different resistance) are connected in series, what do we know about the current in each component. 9. What is the total potential difference across all of the components in question 8 if the potential difference from the power supply is 30 V? Answer By measuring the current through it and the potential difference across it. V=IXR Where V is the voltage in volts (V), I is the current in amperes (A) and R is the resistance in ohms (. 20 V It will be smaller. The potential difference is the sum of the potential difference of each cell so 3 + 3 + 3 + 3 = 12 V 0 V (no current will flow) Total resistance is the sum of the resistance in each component so 2 + 2 + 2 = 6 It will be the same. 30 V (because the total potential difference of the supply is shared across all components in a parallel circuit) Question Date: Date: Date: Date: Date: Date: Date: Date: Date: Date: Date: Date: Date: 1 2 3 4 5 6 7 8 9 P2.3 Currents in electrical circuits_4 Key Recall Question Answer 1. If components are connected in a parallel circuit what do we know about the potential difference? 2. If there is a 20 V cell and two lamps (with different resistance) connected in parallel to the cell, what would the potential difference across each lamp be? 3. If the current through lamp in the first branch of the circuit is 4 A and the second branch is 10 A, what is the total current in the whole circuit? 4. Which component does this current-potential difference graph represent and why? The potential difference across each component is the same. 5. Can you explain ‘resistance’? An electric current flows when electrons move through conductors. As they move through the conductor they collide with ions, this collision between electron and ion in the conductor is what causes resistance. Electrons collide with ions more frequently (as there are more ions for them to collide with) Because there are fewer electrons to carry the current in a thin wire and these will collide with the ions. 6. Why does increasing the length of a wire increase resistance? 7. Why does a thin wire have a higher resistance than a thick wire? 20 V across each lamp The total current in a parallel circuit is the sum of the currents through the separate components so 10 + 4 = 14 A A filament bulb because the graph shows that the resistance of the filament bulb increases as the temperature of the bulb increases. Question Date: Date: Date: Date: Date: Date: Date: Date: Date: Date: Date: Date: Date: 1 2 3 4 5 6 7 P2.3 Currents in electrical circuits_5 Key Recall Question Answer 1. What component does this graph represent and why? A diode, because it shows current only flowing in one direction, the diode has a very high resistance in the reverse direction. 2. How do Light Emitting Diodes (LEDs) work? They only emit light when current flows through in the forward direction. Because they use a much smaller current than other forms of lighting. In small lights (e.g torches) and indicator lights in electrical equipment (e.g. computers and TVs) The resistance decreases as light intensity increases. 3. Why are LEDs becoming more popular? 4. Can you give an example of how LEDs are used? 5. How does the resistance of a light dependent resistor (LDR) vary with light intensity? 6. Can you give an example of how LDRs might be used? 7. How does the resistance of a thermistor vary as temperature increases? 8. Can you give an example of how thermistors might be used? 9. Can you explain how a thermistor in a fire alarm might work? To switch lights on when it starts to get dark. The resistance decreases. In thermostats which regulate central heating and fire alarms. As the temperature increases, the resistance in the thermistor decreases so current flows. This allows current to flow around the circuit to sound the alarm. Question Date: Date: Date: Date: Date: Date: Date: Date: Date: Date: Date: Date: Date: 1 2 3 4 5 6 7 8 9 P2.4 Using mains electricity safely and the power of electrical appliances_1 Key Recall Question Answer 1. What is direct current (d.c.)? 2. What sorts of power supplies produce direct current? 3. What is alternating current (a.c.)? 4. What sort of power supplies produce alternating current? 5. What sort of electricity is represented by this oscilloscope trace? Current that always passes in the same direction. Cells and batteries. 6. If the above oscilloscope trace represents 1 second, what is the frequency of the supply? 7. What is the frequency and potential difference of mains electricity? 8. How are most electrical appliances connected to mains electricity? 9. Which two wires are always found in electrical cables? 10. Which third wire is often found in electrical cables? 11. Why do some wires not have an Earth wire? 2 cycles per second (hertz) Current which is constantly changing direction. Main electricity. a.c. 50 hertz and 230 V (approx) Using cable and three pin plugs. Live and neutral Earth Because the appliance they are attached to have plastic casing (double insulated) or the live wire cannot touch the casing. Therefore they cannot cause electric shocks. Question Date: Date: Date: Date: Date: Date: Date: Date: Date: Date: Date: Date: Date: 1 2 3 4 5 6 7 8 9 10 11 P2.4 Using mains electricity safely and the power of electrical appliances_2 Key Recall Question 1. What are mains electricity cables made from and why? 2. What colour is the neutral wire? 3. What colour is the Earth wire? 4. What colour is the live wire? 5. What are the pins in an electric plug made of and why? 6. How are the three wires in the cable wired up in the three pin plug? 7. What is the role of a fuse in the plug? 8. If a device works at 4 A, should there be a 3 A, 5 A or 13 A fuse in the plug? 9. Simply, how do residual current circuit breakers (RCCB) work? 10. What is the advantage of an RCCB over a fuse? 11. Why are some appliances with metal casings ‘earthed’? Answer The outside layer is made from plastic because it is a good, flexible insulator so should not give electric shocks. The two or three wires inside are made from copper as they are good conductors. Blue Green and yellow stripes Brown Brass, because they are good conductors. Blue goes left, brown goes right, striped goes to the top. The fuse is connected to the live wire so if the current gets too high the fuse will melt and disconnect the circuit. A 5 A (the fuse which is closest to the current in the device but above it) They detect a difference between the current in the live wire and the neutral wires. They work much faster. Because the earth wire is connected to the metal casing so should the live wire touch the casing, the electricity has a safe route to pass through the earth wire and not cause electric shock. Question Date: Date: Date: Date: Date: Date: Date: Date: Date: Date: Date: Date: Date: 1 2 3 4 5 6 7 8 9 10 11 P2.4 Using mains electricity safely and the power of electrical appliances_3 Key Recall Question 1. What happens to a resistor when an electrical charge flows through it? 2. What advantages do power saving lamps such as Compact Fluorescent Lamps (CFLs) have over filament bulbs? 3. What do you call the rate at which energy is transferred in an appliance? 4. How do you calculate the rate at which energy is transferred in an appliance? 5. If a lamp transfers 2000 J in 10 seconds what is its power? 6. Which equation links power, potential difference and current? 7. If an appliance has a power of 2.3 kW and the potential difference of 230 V, what is its current? 8. Would a 3 A, 5 A or 15 A fuse be most suitable for the appliance in question 7? 9. How are energy transferred, potential difference and charge related? Answer It gets hot They waste less energy through heat so that are more efficient and cost less to run. Power P = E/t Where P is power in watts (W), E is energy in joules (J) and t is time in seconds (s) P = E/t P = 2000/10 = 200 W P=IXV Where P is power in watts (W), I is current in amperes (A) and V is potential difference in volts (V) P = I X V so I = P/V (remember 1 kW = 1000 W) I = 2300/230 I = 10 A 13 A E=VXQ Where E is energy in joules (J), V is potential difference in volts (V) and Q is charge in coulombs (C). Question Date: Date: Date: Date: Date: Date: Date: Date: Date: Date: Date: Date: Date: 1 2 3 4 5 6 7 8 9 P2.5 What happens when radioactive substances decay and the uses and dangers of their emissions_1 Key Recall Question Answer 1. What does the nuclear model of the atom look like? 2. Which scientists used scattering experiments to help discover the nuclear model of the atom and change scientists from thinking about the ‘plum pudding’ model? 3. According to the nuclear model, what is most of the atom? 4. What are the relative masses and charges of protons, neutrons and electrons? The atom consists of a small central nucleus composed of protons and neutrons surrounded by electrons. Rutherford and Marsden 5. What is important about the numbers of electrons and protons in an atom? 6. What do atoms gain or lose to form ions? 7. What is an isotope? 8. What is the atomic number? 9. What is the mass number? 10. Why are some substances radioactive? Empty space Proton; mass = 1 and charge = +1 Neutron; mass = 1 and charge = 0 Electron; mass = negligible and charge = -1 They are equal so the atom has no overall charge. Electrons. An atom which has different numbers of neutrons (the atom always has the same number of protons and electrons) The total number of protons in an atom. The total number of protons and neutrons in the atom. Because they give out radiation from their nuclei all of the time, whatever happens to them. Question Date: Date: Date: Date: Date: Date: Date: Date: Date: Date: Date: Date: Date: 1 2 3 4 5 6 7 8 9 10 P2.5 What happens when radioactive substances decay and the uses and dangers of their emissions_2 Key Recall Question 1. Where does background radiation come from? 2. What are the three types of radiation emitted by a radioactive substance? 3. What is alpha radiation? 4. What is beta radiation? 5. What is gamma radiation? 6. Radon (atomic number 86, mass number 219) decays to polonium by releasing an alpha particle. What is the atomic number and mass number of polonium? 7. Which type of radiation is the most penetrating? 7. Which type of radiation can be stopped by a sheet of paper? 8. Which type of radiation is only stopped by many centimetres of lead? 9. What can stop beta radiation? 10. Which two types of radiation are deflected by electric and magnetic fields and why? 11. Which type of radiation is most ionising? Answer Natural sources (e.g. rocks and cosmic rays from space) and man-made sources (e.g. fallout from nuclear weapons tests and nuclear accidents) Alpha, beta and gamma. Two neutrons and two protons (a helium nucleus) A (high energy) electron from the nucleus Electromagnetic radiation Atomic number = 84 and mass number = 215. (because an alpha particle has two neutrons and two protons) Gamma Alpha Gamma Aluminium Alpha and beta, because they consist of charged particles. Alpha (ionisation means it can knock electrons off atoms, particularly problematic if this happens to atoms in DNA as it can lead to cancer) Question Date: Date: Date: Date: Date: Date: Date: Date: Date: Date: Date: Date: Date: 1 2 3 4 5 6 7 8 9 10 11 P2.5 What happens when radioactive substances decay and the uses and dangers of their emissions_2 Key Recall Question 1. If a radioactive substance is absorbed inside the body, which is most dangerous and why? 2. Which is the most dangerous radioactive source outside the body and why? 3. Can you give some examples of how radiation is used? Answer Alpha because it is the most ionising and easily absorbed by cells (beta and gamma are not easily absorbed) Beta and gamma because they are the most penetrating (alpha is not likely to reach cells inside) Smoke detectors, sterilising equipment, killing cancer cells, dating rocks, chemical tracers in medicine and measuring the thickness of materials in industry. 4. Which types of radiation is most likely to be Beta and gamma, because they are less likely to be used as a medical tracer and why? absorbed by cells so more likely to pass out of the body. 5. What is the half life of a radioactive The average time it takes for the number of nuclei of the material? isotope in a sample to halve, or the time it takes for the count rate from a sample to fall to half its initial level. 6. Francium 223 has a half life of 20 minutes. 0 minutes = 80 cpm If the starting material 80 counts per minute, 20 minutes = 40 cpm what would the counts per minute of 40 minutes = 20 cpm Francium be after 1 hour? 1 hour = 10 cpm 7. Can you describe how to use a graph You look at the 0 time point and find the counts per showing the counts per minute and time a minute (this is the maximum) then half this and use the substance takes to decay to find the half life? counts per minute axis to draw a line across to the half life curve and, from this point, down to the time. This gives you the half life. Question Date: Date: Date: Date: Date: Date: Date: Date: Date: Date: Date: Date: Date: 1 2 3 4 5 6 7 P2.6 Nuclear fission and nuclear fusion_1 Key Recall Question 1. Are nuclear power stations an example of the use of nuclear fission or nuclear fusion? 2. What is nuclear fission? 3. Which two radioactive materials are commonly used in nuclear reactors of power stations? 4. What must the radioactive materials in a nuclear reactor first do for fission to occur? 5. What happens when a nucleus in a reactor undergoes nuclear fission? 6. What do the neutrons produced by nuclear fission produce? 7. What is nuclear fusion? 8. Where is nuclear fusion most likely to be observed? 9. How do stars form? 10. How do planets from? Answer Nuclear fission The splitting of atomic nuclei. Uranium-235 and plutonium-239 Absorb a neutron. The nucleus splits into two smaller nuclei and two or three neutrons. Energy is also released (which is the point in a nuclear power station) A chain reaction (the neutrons go on to be absorbed by more uranium or plutonium nuclei). The joining of two atomic nuclei. In the stars. When enough dust and gas from space is pulled together by gravitational attraction. When smaller masses are formed and are attracted by larger masses due to the gravitational attraction. Question Date: Date: Date: Date: Date: Date: Date: Date: Date: Date: Date: Date: Date: 1 2 3 4 5 6 7 8 9 10 P2.6 Nuclear fission and nuclear fusion_2 Key Recall Question Answer 1. What is special about a star during its ‘main sequence’ and why does this happen? 2. What is the life cycle of a star determined by? 3. A star is first formed from its protostar then continues into the main sequence. After this it can then go through two pathways depending on the size. What is the pathway for stars which are similar in size to the sun? 4. What is the pathway for stars which are much bigger than the sun? 5. What else do the nuclear fusion processes in the stars produce? 6. How are elements distributed across the universe? 7. How are stars able to maintain their energy output for millions of years? It is stable because the forces within the star are balanced. 8. Which elements can be made in the main sequence of a star? 9. Which elements are formed in supernovas? Its size (protostar main sequence) red giant white dwarf black dwarf (protstar main sequence) red super giant supernova neutron star or black hole All of the naturally occurring elements By an explosion of a massive star (supernova) at the end of its life. Hydrogen atoms are fused to form helium atoms which releases energy. These fusion reactions can continue to form bigger elements so this can carry on for millions of years. Elements up to iron. Elements heavier then iron. Question Date: Date: Date: Date: Date: Date: Date: Date: Date: Date: Date: Date: Date: 1 2 3 4 5 6 7 8 9