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S4 Physics: Newton’s Laws of Motion Paper 1 (F = ma and inertia)
S4 Physics: Newton’s Laws of Motion Paper 1 (F = ma and inertia)
Paper 1 drills the second law: net force, mass and acceleration, any two giving the third, then inertia in plain words.
Quick answer 3 m/s2; 20 N; inertia depends on mass; zero net force; 24 N; 3 m/s2; 175 N; 720 N; 5 m/s2; zero net force does not mean at rest.
01 Paper details (check answers afterwards)
| Item | Detail |
|---|---|
| Questions | 10 questions |
| Suggested time | 25 minutes |
| Difficulty mix | Foundation 4 · Intermediate 3 · Challenge 2 · Error redo 1 |
| Chapter | Chapter: S4 Physics: Newton’s Laws of Motion |
| Level | S4 |
02 Questions (10 items)
- FoundationA 4 kg body feels a net force of 12 N. Find its acceleration.
- FoundationA 5 kg body accelerates at 4 m/s². What net force acts on it?
- FoundationWhat determines the size of inertia?
- FoundationA body moves in a straight line at a steady 5 m/s. What is the net force on it?
- IntermediateAn 8 kg body starts from rest and reaches 12 m/s in 4 s. Find the net force.
- IntermediateA 12 N horizontal pull acts on a 3 kg block while friction is 3 N. Find the acceleration.
- IntermediateA 0.5 kg ball hits a wall at 20 m/s and rebounds at 15 m/s after 0.1 s. Find the average force from the wall.
- ChallengeA 60 kg person stands on a scale in a lift accelerating upward at 2 m/s², with g taken as 10 m/s². Find the reading.
- ChallengeA 2 kg body feels 6 N and 8 N at right angles. Find its acceleration.
- Error redoA student writes that zero net force means the body must be at rest. What is wrong?
03 Answers and one-line notes
| # | Answer | One-line note |
|---|---|---|
| 1 | 3 m/s² | The second law gives a as F over m, so 12 over 4 is 3 m/s2. |
| 2 | 20 N | F equals m times a, so 5 times 4 gives 20 N along the acceleration. |
| 3 | The mass, with larger mass giving larger inertia | Inertia is the resistance to a change of motion and depends only on mass, not on speed or shape. |
| 4 | Zero, that is 0 N | By the first law a constant velocity means zero acceleration, so the net force must vanish. |
| 5 | 24 N | The acceleration is 12 over 4, or 3 m/s2, and 8 times 3 gives 24 N. |
| 6 | 3 m/s² | The net force is 9 N, so 9 over 3 gives 3 m/s2 against the friction. |
| 7 | 175 N | The change of velocity is 35 m/s because the direction reverses, so 0.5 times 35 over 0.1 is 175 N. |
| 8 | 720 N | The reading equals the normal force, and R minus mg equals ma, so 60 times 12 gives 720 N. |
| 9 | 5 m/s² | The resultant is the square root of 36 plus 64, or 10 N, so 10 over 2 gives 5 m/s2. |
| 10 | Zero net force allows rest or steady straight-line motion. | The first law covers both cases, since only the acceleration is zero while the velocity may be a non-zero constant. |
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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