Physics A level Induction Day Exam

Transcription

1 Physics A level Induction Day Exam Name (in block capitals):. Current School (in block capitals): I studied Double / Triple science (delete as appropriate) Marks gained.. out of 45 Percentage Q. The graph shows how the electric current through a 2 V filament bulb varies with the potential difference across the bulb. (a) What is the meaning of the following terms? electric current potential difference The resistance of the metal filament inside the bulb increases as the potential difference across the bulb increases. Explain why Page

2 (c) Use data from the graph to calculate the rate at which the filament bulb transfers energy, when the potential difference across the bulb is 6 V. Using the correct equation from Physics equation sheet. Show clearly how you work out your answer Rate of energy transfer =... W (Total 7 marks) Q2.The figure below shows a skateboarder jumping forwards off his skateboard. The skateboard is stationary at the moment the skateboarder jumps. (a) The skateboard moves backwards as the skateboarder jumps forwards. Explain, using the idea of momentum, why the skateboard moves backwards The mass of the skateboard is.8 kg and the mass of the skateboarder is 42 kg. Calculate the velocity at which the skateboard moves backwards if the skateboarder jumps forwards at a velocity of 0.3 m / s. Using the correct equation from Physics equation sheet.... Page 2

3 Q3.A student rubs an acetate rod with a cloth. Velocity of skateboard =... m / s (Total 6 marks) Figure shows the charges on the acetate rod and cloth before and after rubbing. Figure (a) Explain how rubbing an acetate rod with a cloth causes the rod and cloth to become charged. After charging them, the student moves the acetate rod and the cloth closer together. Which statement is correct? Tick one box. There is no force between the acetate rod and the cloth. Page 3

4 There is a force of attraction between the acetate rod and the cloth. There is a force of repulsion between the acetate rod and the cloth. Give a reason for your answer. (c) Figure 2 shows a Van de Graaff generator, which is used to generate static electricity. Figure 2 The longer the Van de Graaff generator is switched on, the more charge is stored on the metal dome. Complete the sentence. The amount of charge on the metal dome is increased, which causes the potential difference between the metal dome and the earthed sphere to.... () (d) When the potential difference between the Van de Graaff generator and the earthed sphere is 60 kv, a spark jumps between the metal dome and the earthed sphere. The spark transfers coulombs of charge to the earthed sphere. The equation which links charge, energy and potential difference is: energy transferred = charge potential difference Calculate the energy transferred by the spark. Page 4

5 Energy transferred =... J (Total 8 marks) Q4. The diagram shows a sky-diver in free fall. Two forces, X and Y, act on the sky-diver. (a) Complete these sentences by crossing out the two lines in each box that are wrong. (i) Force X is caused by. () Force Y is caused by. () The size of force X changes as the sky-diver falls. Describe the motion of the sky-diver when: (i) force X is smaller than force Y, force X is equal to force Y. () (Total 5 marks) Q5. (a) The graph shows how a sample of barium-43, a radioactive isotope with a short half-life, decays with time. Page 5

6 (i) What is meant by the term isotope? () What is meant by the term half-life? () (iii) Use the graph to find the half-life of barium-43. Half-life =... seconds () (i) Humans take in the radioactive isotope carbon-4 from their food. After their death, the proportion of carbon-4 in their bones can be used to tell how long it is since they died. Carbon-4 has a half-life of 5700 years. A bone in a living human contains 80 units of carbon-4. An identical bone taken from a skeleton found in an ancient burial ground contains 5 units of carbon-4. Calculate the age of the skeleton. Show clearly how you work out your answer. Page 6

7 Age of skeleton =... years Why is carbon-4 unsuitable for dating a skeleton believed to be about 50 years old? () (c) The increased industrial use of radioactive materials is leading to increased amounts of radioactive waste. Some people suggest that radioactive liquid waste can be mixed with water and then safely dumped at sea. Do you agree with this suggestion? Explain the reason for your answer. (Total 9 marks) Q6.Figure shows an exercise device called a chest expander. The three springs are identical. Figure A person pulls outwards on the handles and does work to stretch the springs. (a) Complete the following sentence. When the springs are stretched energy is stored in the springs. () Figure 2 shows how the extension of a single spring from the chest expander depends on the force acting on the spring. Figure 2 Page 7

8 (i) How can you tell, from Figure 2, that the limit of proportionality of the spring has not been exceeded? () Use data from the graph in Figure 2 to calculate the spring constant of the spring. Give the unit. Spring constant =... Unit... (iii) Three identical resistors joined in parallel in an electrical circuit share the total current in the circuit. In a similar way, the three springs in the chest expander share the total force exerted. By considering this similarity, use Figure 2 to determine the total force exerted on the chest expander when each spring is stretched by 0.25 m. Total force =... N (c) The student in Figure 3 is doing an exercise called a chin-up. Figure 3 Page 8

9 Each time the student does one chin-up he lifts his body 0.40 m vertically upwards. The mass of the student is 65 kg. The student is able to do 2 chin-ups in 60 seconds. Calculate the power developed by the student. Gravitational field strength = 0 N/kg Power =... W (Total 0 marks) Page 9

10 M. (a) electric current (rate of) flow of (electric) charge / electrons accept with Q and t correctly named potential difference work done / energy transferred per coulomb of charge (that passes between two points in a circuit) accept with W and Q correctly named metals contain free electrons (and ions) accept mobile for free as temperature of filament increases ions vibrate faster / with a bigger amplitude accept atoms for ions accept ions/atoms gain energy accept vibrate more for vibrate faster do not accept start to vibrate electrons collide more (frequently) with the ions or (drift) velocity of electrons decreases do not accept start to collide accept increasing the p.d. increases the temperature ( mark) and (and) resistance increases with temperature ( mark) if no other marks scored (c) 7.8 allow mark for obtaining value.3 from graph or allow mark for a correct calculation using an incorrect current in the range.2-.6 inclusive 2 [7] M2.(a) momentum before (jumping) = momentum after (jumping) accept momentum (of the skateboard and skateboarder) is conserved before (jumping) momentum of skateboard and skateboarder is zero accept before (jumping) momentum of skateboard is zero accept before (jumping) total momentum is zero after (jumping) skateboarder has momentum (forwards) so skateboard must have (equal) momentum (backwards) answers only in terms of equal and opposite forces are insufficient Page 0

11 7 accept 7 for 3 marks allow 2 marks for momentum of skateboarder equals 2.6 or 0 = (.8 v) or allow mark for stating use of conservation of momentum 3 [6] M3.(a) Level 2 (3 marks): A detailed and coherent explanation is provided. The student makes logical links between clearly identified, relevant points. Level ( 2 marks): Simple statements are made, but not precisely. The logic is unclear. 0 marks: No relevant content Indicative content friction (between cloth and rod) causes electrons (to) move from the acetate rod or to the cloth (net) charge on cloth is now negative (net) charge on rod is now positive Maximum of 3 marks there is a force of attraction between the acetate rod and the cloth (reason) unlike charges attract or (c) negative charges attract positive charges increase (d) (J) accept.5 (J) with no working shown for 2 marks. (a) (i) friction accept any way of indicating the correct answer [9] gravity accept any way of indicating the correct answer Page

12 (i) accelerates or speed / velocity increases accept faster and faster ( mark) do not accept faster pace / falls faster or suggestions of a greater but constant speed downwards / falls accept towards the Earth / ground this may score in part if it does not score here and there is no contradiction between the two parts constant speed / velocity or terminal velocity / speed or zero acceleration stays in the same place negates credit [5]. (a) (i) element with equal number of protons, different number neutrons or same atomic/proton number different mass/nuclear number (iii) time taken for activity or count rate or number of nuclei to decrease to half accept parents atoms or radioactive isotope do not accept time taken for radioactivity/substance/ material to halve 2 (s) (i) (years) allow mark for iterative steps or statement of 4 half-lives 2 (c) FOR decay (of carbon 4) over 50 years is insignificant accept very little decay accept change is too small either argument gains full credit accept any 3 valid points from for and/or against arguments massive dilution of waste reduces concentration (within a given volume) to insignificant levels distant from habitation AGAINST pollution (of the sea/beach) mutation or harm caused to living things (animals/plants) effect on food chain long period of time necessary Page 2

13 M6.(a) elastic potential 3 [9] (i) line is straight accept line does not curve 400 allow mark for correct substitution of any pair of numbers correctly taken from the graph e.g.60 = k newtons per metre or N/m if symbols are used they must be correct (iii) 300 allow mark for correctly obtaining force on spring = 00N 2 (c) 52 allow 2 marks for calculating change in gpe for chin-up as 260 (J) or for 2 chin-ups as 320 (J) an answer 4.3 gains 2 marks allow mark for correct substitution into gpe equation ie gpe = ( 2) or correct use of power equation with an incorrect value for energy transferred 3 [0] Page 3