Grade 11 Physical Sciences · Mechanics

Explain using Newton's laws

Explain everyday events in words using Newton's laws, for example why a seatbelt stops a passenger from moving forward when a car brakes.

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Newton's First Law of Motion grade 11 and 12 PhysicsMiss Martins Maths and Science

Newton's Third Law of Motion Grade 11 and 12 PhysicsMiss Martins Maths and Science

Elevator Physics Problem - Normal Force on a Scale & Apparent WeightThe Organic Chemistry Tutor

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Question 1.1 · November 2025 · Paper 1 · National (DBE) · 2 marks

Various options are provided as possible answers to the following questions. Each question has only ONE correct answer. Choose the answer and write only the letter (A–D) next to the question numbers (1.1 to 1.10) in the ANSWER BOOK, e.g. 1.11 E.

1.1 The net force acting on an object on a horizontal surface is always ...(2)

A in the direction of motion of the object.
B in the direction of acceleration of the object.
C zero when the object moves at constant acceleration.
D increasing when the object moves at constant acceleration.

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More past paper questions: explain using newton's laws

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3. Question 1.1 · May/June 2024 · Paper 1 · National (DBE) · 2 marks
Various options are provided as possible answers to the following questions. Each question has only ONE correct answer. Choose the answer and write only the letter (A–D) next to the question numbers (1.1 to 1.10).
1.1 A book rests on a table. Which ONE of the following forces will form an action-reaction pair with the weight of the book?(2)
1. A Force of the Earth on the book
2. B Force of the book on the Earth
3. C Force of the book on the table
4. D Force of the table on the book
Show the memo (1 tick)Memo
1. ✓
  Choose the correct optionThe weight of the book is the force of the Earth on the book. Its Newton III partner is the same type of force with the two objects swapped: the force of the book on the Earth (equal in size, opposite in direction).
  
  The force of the table on the book (D) is the normal force. It also balances the weight, but it acts on the same object (the book) and is a different type of force, so it is not the action-reaction partner.
  
  Answer: B
  2 marks · Explain using Newton's laws
4. Question 1.4 · May/June 2023 · Paper 1 · National (DBE) · 2 marks
Various options are provided as possible answers to the following questions. Each question has only ONE correct answer.
1.4 The magnitude of the gravitational force that spheres X and Y exert on each other is F.

The mass of sphere X is now doubled while the mass of sphere Y and the distance between the centres of the spheres remain the same.

Which ONE of the following combinations is CORRECT for the magnitude of the forces that the spheres now exert on each other?(2)
1. A Force that X exerts on Y: F; force that Y exerts on X: F
2. B Force that X exerts on Y: F; force that Y exerts on X: 2F
3. C Force that X exerts on Y: 2F; force that Y exerts on X: F
4. D Force that X exerts on Y: 2F; force that Y exerts on X: 2F
Show the memo (1 tick)Memo
1. ✓
  Correct option $F = \frac{G m _{1} m _{2}}{r ^{2}}$ : doubling one mass doubles the force, so the force becomes 2F. By Newton\'s third law the force X exerts on Y and the force Y exerts on X are always equal in magnitude, so BOTH are 2F.
  
  Answer: D
  2 marks · Explain using Newton's laws
5. Question 1.1 · November 2023 · Paper 1 · National (DBE) · 2 marks
Various options are provided as possible answers to the following questions. Each question has only ONE correct answer.
1.1 A constant net force is applied to a block. Which ONE of the following statements is CORRECT?

The block will move with a ...(2)
1. A constant velocity.
2. B constant acceleration.
3. C constantly increasing acceleration.
4. D constantly decreasing acceleration.
Show the memo (1 tick)Memo
1. ✓
  Correct optionBy Newton's second law $F_{n e t} = ma$ , so $a = \frac{F _{n e t}}{m}$ . If $F_{n e t}$ and $m$ stay constant, the acceleration is constant. A constant velocity (A) would need zero net force.
  
  Answer: B
  2 marks · Explain using Newton's laws
6. Question 1.1 · May/June 2022 · Paper 1 · National (DBE) · 2 marks
Various options are provided as possible answers to the following questions. Each question has only ONE correct answer. Choose the answer and write only the letter (A–D) next to the question numbers (1.1 to 1.10) in the ANSWER BOOK, e.g. 1.11 E.
1.1 A bucket is at rest on a table.

Which ONE of the following is the reaction force to the weight of the bucket, as described by Newton's Third Law?(2)
1. A Force of the table on Earth
2. B Force of the bucket on Earth
3. C Force of the bucket on the table
4. D Force of the table on the bucket
Show the memo (1 tick)Memo
1. ✓
  Choose the correct optionThe weight of the bucket is the force of the EARTH on the BUCKET. Its Newton III partner swaps the two bodies: the force of the BUCKET on the EARTH. D (table on bucket) is the normal force; it balances the weight, but it acts on the same body, so it is not the action-reaction partner.
  
  Answer: B
  2 marks · Explain using Newton's laws

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