P3 Formulas and Questions
There are 9 formulas you will get on P3. They are given to you at the start of the exam but you may find it helpful to learn them.
Formula 1:
1. Calculate the intensity of a 100 W beam of radiation spread over an area of 5 cm2 (H)
2. Calculate the intensity of a laser pointer with a power output of 1.0 × 10 -3 W (1 mW) on a board if the dot is a square measuring 1 mm by 1 mm. (H)
3. If the intensity of a torch’s beam is 6 W/m2 over an area of 4 m2, what was the power output of the bulb?(H)
4.a) A typical laser used in sight correction will transfer 1 mJ of energy (1 × 10–3 J) in a 10 ns (10 × 10–9 s) pulse. What is the power output of the laser in watts (1 W=1 J/s)? (Use the familiar equation Power =Energy/time) (H)
b) b If this laser beam was directed into an area 100 μm × 100 μm (100 × 10–6 m × 100× 10–6 m), what would the intensity of the light be?(H)
Formula 2:
5. What is the power of a lens with a focal length of:
a) 0.1 m .b) 20 cm .c) 5 cm?
6. The combination of lens and cornea in the human eye has a power of about 60 D. What is the focal length?(H)
Formula 3:
7. A light bulb is placed 20 cm from a lens with a focal length of 10 cm.Where will an image form? (H)
8. A pupil sits 100 cm from a converging lens with a focal length of 5 cm. Where will her image be formed? (H)
9. A magnifying glass with a focal length of 5 cm is used to examine a postage stamp 3 cm away.
a) Where will the image be formed? (H)
b) What indicates the image is virtual? (H)
You will not receive this formula:
10. A light ray approaches a glass block at 30° to the normal. The refractive indices of air and water are 1 and 1.5 respectively At what angle will the light be refracted?(H)
11. A light ray travelling from water to air approaches the surface at 20° to the normal. If the refractive index of air is 1 and that of water is 1.33, what will the angle of refraction be? (H)
12. Calculate the critical angle for perspex of refractive index 1.48 when in air. (H)
13. a) Calculate the critical angle at the interface between glass (refractive index = 1.5) and water (refractive index = 1.33). (H)
b) Explain why it is greater than the critical angle for glass in air. (H)
(H) Formula 4:
14. (H) The charge on an electron is 1.6 × 10–19 C. Calculate the current when the number of electrons flowing is:
a)2 × 1014 per second
b) 9.4 × 1015 per second
Formula 5:
15.(For this question, use the equation Current = Charge/time from P2)
The charge on an electron is 1.6 × 10–19 C. Calculate the current when the number of electrons flowing is:
a) 2 × 1014 per second(H)
b) 9.4 × 1015 per second (H)
16. a)What is the kinetic energy of an electron when the potential differenceis 100 kV? (H)
b) The mass of an electron is 9.11 × 10–31 kg. What is the velocity of the electron in part a? (H)
Formula 6:
17. A wave has a period of 3 seconds, what is it’s frequency?
18. A wave has a period of 20ms, what is it’s frequency? (H)
19. What is the period of a wave that has a frequency of 40Hz? (H)
(H) There is no set formula for balancing nuclear equations, but I have included these questions for extra practice:
20. → +
21. → +
22. → +
23. → +
24. → +
25. → +
26. → +
27. → +
28. → +
29. → +
There is no set formula for proving the quark make up of protons and neutrons, but these questions are for extra practice:
Use the table below for the following questions
Quark / Up / DownMass / /
Charge / /
30. What is the quark make up of a proton? Prove this using the table
31. What is the quark make up of a neutron? Prove this using the table
32. Balance the following equation and state what kind of decay it is,explaining it in terms of quarks
→ +
33. Balance the following equation and state what kind of decay it is,
explaining it in terms of quarks
→ +
You will not receive this equation in P3, as you are expected to remember it from P2!
34. What is the momentum of a lorry with a mass 1400kg travelling at 20m/s?
35. What is the momentum of a car with a mass 400kg travelling at 5m/s?
36. If a 2g flea has a momentum of 0.3 kgm/s, what is its velocity?(H)
37. (H) A man of mass 80 kg is running at a steady velocity of 4 m/s. He doesn’t watch where he is going and bumps into a stationary shopping trolley full of shopping, getting stuck to it in the process. The new combined mass of him and the shopping trolley is 120 kg. What velocity do the man, the trolley and the shopping have now? (You may draw a diagram for support)
38. (H) A runner is not looking where he is going. He runs into a stationary bus. The boy has a mass of 48 kg and his velocity dropped from 4.2 m/s to zero.
a)What was his momentum whilst running?
b) What was velocity of the 16 tonne bus after collision? (1 tonne = 1 000 kg)(You may draw a diagram for support)
There is no shared formula for converting between celcius and kelvin, but this will help:
Tkelvin= TCelcius+ 273
39. What are the following temperatures on the Celcius scale?
a) 500Kb) 100K
40. What are the following temperatures on the Kelvin scale?
a) 0oCb) 27 oC
Formula 7:
41. A toy balloon is taken from a room and put into a freezer. In the room, the balloon’s volume is 1500 cm3. The pressure does not change. The room temperature is 17 °C and the freezer temperature is –13 °C. What is the volume of the balloon in the freezer? (Remember to convert to kelvin!)
42. 300cm3 of oxygen is held at 25˚C. The pressure is kept the same. The
volume is reduced to 225cm3, what is the new temperature in ˚C?
Formula 8:
43. You start off with 200ml of oxygen at a pressure of 20Pa.
You increase the pressure to 27Pa what volume will you have now?
44. What volume of gas (at atmospheric pressure) is stored at 230 000 000 Pa in a 0.15 m3 bottle?(Atmospheric pressure is approximately 100 000 Pa)
Formula 9:
45. The gas bottle in question 40 is normally stored at 20°C. What is the pressure in the bottle if the temperature rises to 40 °C (Remember to convertto Kelvin)
46. (H) Gas is trapped in a weather balloon. The volume is 2 m3 at ground level where the temperature is (27 °C) and the pressure is 150 000 Pa. At a high altitude, the temperature falls to 240 K (–33 °C) and the pressure drops to 30 000 Pa. Calculate the new volume.
Answers:
1)200 000W/m2 . 2) 1000 W/m2 .3) 24W .4.a) 100 000W (= 100 kW) .4.b) 1 × 1013 W/m2 .5.a) 10D .5.b) 5D .5.c) 20D .6) 0.0167 m (i.e. 1.67 cm) .7) 20 cm .8) 5.3cm .9.a) -7.52 cm .9.b) It has a negative value .10) 19.3o .11) 27.1o .12) 42.5o .13.a) 62.5o .13.b) It is greater because there is less of a difference between the refractive indices – less of a difference between the speeds of the ray in the two media. .14.a) 3.2 × 10–5 A .14.b) 1.5 × 10–3 (=1.5 mA)
.15.a) 3.2 × 10–5 A .15.b) 1.5 × 10–5 A (=1.5mA) .16.a) 1.6 × 10–14 J .16.b) 1.87 × 108 m/s .17) 0.33Hz
.18) 50Hz .19) 0.025s (=25ms)
.30) uud (Charges== 1. Mass=++=1 )
.31) udd (Charges== 0. Mass=++=1)
.32) Beta-minus decay. A down quark changes in to an up quark (because a neutron has changed in proton).
33) Beta-plus decay. An up quark changes in to a down quark (because a proton changes in to a neutron).
.34) 28 000 kg m/s .35) 2 000 kg m/s .36) 150m/s .37) 2.67m/s .38.a) 201.6 kg m/s .38.b) 0.01m/s .39.a) 227 oC .39.b) -173 oC .40.a) 273 K .40.b) 300 K .41) 1344.8 cm3 .42) 223.5 oC .43) 148ml
.44) 345 m3 .45) 245 699 659 Pa .46) 8 m3