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S4 Physics: Newton’s Laws of Motion Paper 2 (weight, normal force and friction)
S4 Physics: Newton’s Laws of Motion Paper 2 (weight, normal force and friction)
Paper 2 handles the vertical bookkeeping: weight, normal force and friction, then puts them into F = ma.
Quick answer 50 N; 7 kg; 96 N while the mass stays 60 kg; 80 N; 60 N; 3 m/s2; 10 m/s; 400 N; 5 m/s2; weight is a force and mass is an amount.
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)
- FoundationWhat is the weight of a 5 kg body on the Earth surface, taking g as 10 m/s²?
- FoundationA body weighs 70 N on Earth. Find its mass, taking g as 10 m/s².
- FoundationA 60 kg astronaut stands on the Moon where g is 1.6 m/s². Give the weight and the mass.
- FoundationAn 8 kg box rests on level ground. Find the normal force from the ground, taking g as 10 m/s².
- IntermediateA 20 kg box on ground with friction coefficient 0.3 is pulled at steady speed. Find the horizontal pull, taking g as 10 m/s².
- IntermediateA 10 kg body has a 50 N horizontal pull and 20 N of friction. Find the acceleration.
- IntermediateA 3 kg ball falls freely from 5 m, ignoring air resistance and taking g as 10 m/s². Find its landing speed.
- ChallengeA 50 kg person stands on a scale in a lift accelerating downward at 2 m/s², with g as 10 m/s². Find the reading.
- ChallengeA 4 kg body has 30 N to the right and 10 N to the left. Give the size and direction of the acceleration.
- Error redoA student writes that their weight is 50 kg. What is wrong?
03 Answers and one-line notes
| # | Answer | One-line note |
|---|---|---|
| 1 | 50 N | W equals mg, so 5 times 10 gives 50 N, a force measured in newtons. |
| 2 | 7 kg | Mass is weight over g, so 70 over 10 gives 7 kg. |
| 3 | Weight 96 N and mass still 60 kg | The weight is 60 times 1.6, or 96 N, while the mass stays 60 kg everywhere. |
| 4 | 80 N | With no other vertical force the normal force balances the weight, so 8 times 10 gives 80 N. |
| 5 | 60 N | Friction is 0.3 times 200, or 60 N, and a steady speed needs a pull of exactly that size. |
| 6 | 3 m/s² | The net force is 30 N, so 30 over 10 gives 3 m/s2. |
| 7 | 10 m/s | The speed squared is 2 times 10 times 5, or 100, so the speed is 10 m/s and mass does not matter. |
| 8 | 400 N | Since mg minus R equals ma, R is 50 times 8, or 400 N, which is less than at rest. |
| 9 | 5 m/s² to the right | The net force is 20 N to the right, so 20 over 4 gives 5 m/s2 in that direction. |
| 10 | Mass is measured in kg while weight is a force in newtons, so 50 kg is a mass and the weight is about 500 N. | The student uses a mass unit for a force, and the two values differ by a factor of g. |
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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