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S4 Physics work, energy and power paper 1: ten formula items
S4 Physics work, energy and power paper 1: ten formula items
Ten items on the basic substitution of work, kinetic energy, potential energy and power, all in DSE units.
Direct answers Items 01 to 05 need one formula each, 06 to 08 mix force with speed, and 09 covers efficiency. Allow 25 minutes, then check section 03.
01 Paper details (check answers afterwards)
| Item | Detail |
|---|---|
| Questions | 10 |
| Suggested time | 25 |
| Difficulty mix | Foundation 3 · Intermediate 3 · Challenge 3 · Error redo 1 |
| Chapter | Chapter: S4 Physics Work, Energy and Power |
| Level | S4 |
02 Questions (10 items)
- FoundationA force of 20 N pushes a box 3 m along the direction of the force. Find the work done.
- FoundationA ball of mass 2 kg moves at 3 m/s. Find its kinetic energy.
- FoundationA book of mass 0.5 kg is lifted 4 m. Find the gain in gravitational potential energy (g = 10 N/kg).
- IntermediateA machine does 300 J of work in 15 s. Find its power output.
- IntermediateA 5 kg dumbbell is lifted 2 m at constant speed. Find the work done (g = 10 N/kg).
- IntermediateA machine pulls an object at a steady 2.5 m/s with a force of 40 N. Find its output power.
- ChallengeA ball of mass 0.4 kg moves at 5 m/s. Find its kinetic energy.
- ChallengeAn object of mass 4 kg is raised 2.5 m. Find the gain in potential energy (g = 10 N/kg).
- ChallengeA machine takes in 300 J and delivers 240 J of useful output. Find its efficiency.
- Error redoA pupil claims that doubling the speed doubles the kinetic energy. What is wrong?
03 Answers and one-line notes
| # | Answer | One-line note |
|---|---|---|
| 1 | 60 J | Work = force x displacement along the force = 20 x 3 = 60 J. |
| 2 | 9 J | Kinetic energy = 1/2 x m x v squared = 1/2 x 2 x 9 = 9 J. |
| 3 | 20 J | mgh = 0.5 x 10 x 4 = 20 J; the height rises, so the stored energy rises too. |
| 4 | 20 W | Power = work / time = 300 / 15 = 20 W. |
| 5 | 100 J | At constant speed the lifting force balances weight: F = mg = 50 N, so W = 50 x 2 = 100 J. |
| 6 | 100 W | Power = force x speed = 40 x 2.5 = 100 W. |
| 7 | 5 J | 1/2 x 0.4 x 25 = 5 J; the speed enters as a square, so it matters most. |
| 8 | 100 J | mgh = 4 x 10 x 2.5 = 100 J. |
| 9 | 80% | Efficiency = useful output / input x 100% = 240 / 300 x 100% = 80%. |
| 10 | Kinetic energy depends on the square of the speed, so doubling the speed gives four times the energy. | 1/2 x m x (2v) squared = 4 x (1/2 x m x v squared), so the factor is four, not two. |
04 What to do after marking
- After marking, redo only the wrong items and write down which step went wrong (formula, unit, or misread number).
- Repeat the same item two days later; move to the next paper only when both attempts are correct.
- Parents only need the answer and note columns; there is no need to explain every item.
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