Physics paper 1

• 1. Define a 'system'.

  1. An object or group of objects
• 2. State the changes to the energy stores for a moving object hitting an obstacle.

  2. The object's kinetic energy is transferred into sound and heat (and possibly permanent deformation).
• 3. State the changes to the energy stores for a book falling from a shelf.

  3. The book's gravitational potential energy store is transferred to its kinetic energy store.
• 4. Write down the equation to calculate gravitational potential energy.


  4. Ep = mgh
• 5. Write down the equation to calculate kinetic energy.


  5. Ek = ½ mv²
• 6. A bag of sugar, mass 2kg, falls from a shelf 2m high. Calculate the bag's gravitational potential energy (a) at the top of its fall and (b) when it hits the floor. (g=9.8N/kg)

  6. (a) Ep = mgh Ep= 2 x 9.8 x 2 = 39.2J (b) Ep = 0J (height is 0m)
• 7. State the value of the bag of sugar's kinetic energy at the instant it strikes the floor.


  7. 39.2J (all of the Ep is converted into Ek)
• 8. Calculate the store of kinetic energy in a toy car of mass 2kg with a velocity of 5m/s.


  8. Ek = ½ mv² = 0.5 x 2 x 5² = 25J
• 9. Calculate the velocity of a ball of mass 0.5kg that has a kinetic energy store of 100J.

  9. Ek = ½ mv² so rearrange to give v = √(2Ek/m) so v = √(2x100/0.5) = 20m/s
• 10. A spring with a spring constant of 40N/m is stretched 20cm. Calculate the energy stored in the spring.

  10. Ee = ½ ke² = 0.5 x 40 x 0.2² = 0.8J
• 11. Define 'specific heat capacity'.

  11. the amount of energy required to raise the temperature of one kilogram of the substance by one degree Celsius
• 12. Write down the equation that links the change in thermal energy with specific heat capacity. Define each term and state its unit.

  12. ᐃE = mcᐃᎾ where ᐃE = energy change in J, m = mass in kg, c is specific heat capacity in J/kg ᴼC and ᐃᎾ is the change in temperature in ᴼC.
• 13. Calculate the change in energy required to raise the temperature of 50g of water from 20ᴼC to 60ᴼC. (c for water = 4200 J/kg ᴼC)


  13. ᐃE = mcᐃᎾ ᐃE = 0.050 x 4200 x 40 = 8400J.
• 14. Define 'power'.


  14. the rate at which energy is transferred or the rate at which work is done
• 15. Write down the equation that links power, work done and time. State the unit of each quantity.


  15. P = E/t or E=Pt Units: E (J), P (W) and t (s)
• 16. Calculate the power of an electric iron that uses 240kJ in 2 minutes.

  16. P = E/t = 240000 / 120 = 2000W or 2kW
• 17. Two electric motors lift two packages using a conveyer belt at a post office. Motor A does 200J of work in 4 seconds, whilst motor B does 300J of work in 5 seconds. Show, using clear calculations that motor B is more powerful.


  17. P = E/t Motor A: P = 200/4 = 50W, Motor B: P = 300/5 = 60W.
• 18. A appliance manufacturer is deciding on the materials for a new kettle's construction. State whether the materials needed for the following roles will need to have a high or low thermal conductivity. (a) lid (b) heating element in the base (c) sides.

  18. (a) low (to insulate) (b) high (c) low.
• 19. Write down the equation for calculating efficiency when supplied with values of energy.

  19. Efficiency = useful output energy ÷ total energy input
• 20. Calculate the efficiency of an LED torch which supplies 5W of power to the electrical circuit, which results in 0.5W of heat being produced.

  20. 4.5W is usefully transferred, so 4.5 ÷5 = 0.9 or 90%
• 21. Name three sources of renewable energy where water drives turbines.

  21. Tidal, hydroelectric, waves
• 22. Name the energy resources which produce greenhouse gases.

  22. Coal, oil, gas, biofuel
• 23. State the difference between a renewable and a non-renewable resource.

  23. Renewable is replenished as it is used, non-renewable isn't
• 24. Draw the circuit symbol and write the name of 4 components that can change their resistance.

  24. Variable resistor, light bulb, thermistor, LDR (and diode if you reverse its connections)
• 25. Define 'electric current'.

  25. Flow of electric charge/rate of flow of charge
• 26. Write down the equation linking current, charge and time. Define each term and state its unit.

  26. Q = I t (Q/charge in coulombs, I/current in A, t/time in seconds)
• 27. Calculate the quantity of charge flow when a 5A current flows for 1 minute.

  27. Q = I t Q = 5 x 60 = 300C
• 28. Explain what happens to the current through a fixed resistor when the p.d. across it is doubled.

  28. V=I R so current doubles as well as R is constant
• 29. State Ohm's law.


  29. V = I R at constant temperature
• 30. Define a series circuit.


  30. A circuit with one loop only
• 31. Define a parallel circuit.

  31. A circuit with more than one loop
• 32. Draw a circuit containing light bulbs in both series and parallel arrangements. Label these parts of the circuit as 'series' and 'parallel' clearly.


  32.

  
• 33. Describe the relationship between the resistance of a wire of constant diameter at constant temperature, and its length.

  33. R is directly proportional to length
• 34. Draw a series circuit containing a 6V cell and three fixed resistors: 1ᘯ, 2ᘯ and 9ᘯ.

  34.
• 35. Calculate the current in the circuit in qu34.

  35. I = V/R I = 6/(1+2+9) = 6/12 = 0.5A
• 36. Calculate the p.d. across each of the resistors in the circuit in qu34.

  36. V = I R V1 = 0.5 x 1 = 0.5V V2 = 0.5 x 2 = 1V V3 = 0.5 x 9 = 4.5V
• 37. Draw a parallel circuit containing a 6V cell and three fixed resistors, one on each loop: 1ᘯ, 2ᘯ and 3ᘯ.

  37.
• 38. Calculate the current through each loop of the circuit in qu37 (a parallel circuit containing a 6V cell and three fixed resistors, one on each loop: 1ᘯ, 2ᘯ and 3ᘯ). Calculate the total current flowing from the cell.


  38. I = V/R I₁ = 6/1 = 6A I₂ = 6/2 = 3A I₃ = 6/3 = 2A Itotal = I₁ + I₂ + I₃ = 6 + 3 + 2 = 11A
• 39. State the p.d. across each loop of the circuit in qu37.

  39. 6V (same across each branch)
• 40. Explain the function of a thermistor.

  40. Resistance increases as temperature decreases