Grade 12 Physical Sciences · Mechanics · Reason with momentum ratios

Reason with momentum ratios Grade 12

Say by what factor momentum, force or impulse changes when the mass, velocity or time is changed, for example doubling the mass and halving the velocity leaves p = mv the same.

questions use it, all grades · 4 past paper, 10 practice: 14 questions use it, all grades · 4 past paper, 10 practice
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Momentum Grade 12 Multiple ChoiceMath and Science Online with Tutor Jele

GRADE 12|PHYSICS|MOMENTUM AND IMPULSE| Multiple-Choice QuestionsBright Minds Academy [BMA]

2)Change momentum gr 12 | IntroKevinmathscience

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Question 1.4 · 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.

1.4 Objects P and Q, with masses m and 2m respectively, have the same momentum, as shown in the diagram.

The velocity of P is ...(2) Diagram for question 1.4

A equal to the velocity of Q.
B half the velocity of Q.
C twice the velocity of Q.
D four times the velocity of Q.

Work it out on paper first. Then mark yourself with the official memo, one tick at a time.

More questions: reason with momentum ratios

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3. Question 1.4 · 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.
1.4 A ball is dropped from height h and strikes the floor with momentum p. The ball is then dropped from height $\frac{1}{2}$ h.

Ignore the effects of air friction.

Which ONE of the following represents the momentum of the ball when it strikes the floor after being dropped from height $\frac{1}{2}$ h?(2)
1. A p
2. B $\frac{1}{2}$ p
3. C $\frac{1}{2}$ p
4. D 2p
Show the memo (2 ticks)Memo
1. ✓
  Correct optionDropped from rest: $v_{f}^{2} = 0 + 2 g Δ y$ , so $v_{f} = 2 g h$ . Halving the height gives $v = 2 g \cdot \frac{1}{2} h = \frac{1}{2} 2 g h$ . Momentum $p = m v$ is proportional to $v$ , so the new momentum is $\frac{1}{2}$ p.
  
  Answer: B
  2 marks · Reason with momentum ratios
4. Question 1.3 · 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.
1.3 A ball is dropped from height $h$ and strikes the floor with momentum $p$ .

Ignore air resistance.

The ball is NOW dropped from height $2 h$ , as shown below.

Which ONE of the following represents the momentum with which the ball NOW strikes the floor?(2)
1. A $p$
2. B $2 p$
3. C $2 p$
4. D $2 p$
Show the memo (2 ticks)Memo
1. ✓
  Choose the correct optionFrom $v_{f}^{2} = v_{i}^{2} + 2 g Δ y$ with $v_{i} = 0$ : $v_{f} = 2 g h$ . Doubling the height gives $v_{f} = 2 g (2 h) = 2 2 g h$ , so the speed and the momentum $p = m v$ are multiplied by $2$ , not by 2.
  
  Answer: B
  2 marks · Reason with momentum ratios
5. Practice · NavyBlue · 2 marks
A trolley of mass $m$ moving at speed $v$ has momentum $p$ . What is the momentum of a trolley of mass $2 m$ moving at speed $3 v$ ?(2)
1. A $\frac{2}{3} p$
2. B $\frac{3}{2} p$
3. C $5 p$
4. D $6 p$
Show the memo (2 ticks)Memo
1. ✓
  Correct option with reason $p = m v$ , so the new momentum is $(2 m) (3 v) = 6 m v = 6 p$ .
  Answer: D
  2 marks · Reason with momentum ratios
6. Practice · NavyBlue · 2 marks
The speed of a cricket ball is doubled while its mass stays the same. Which ONE of the following correctly describes the change in the magnitude of its momentum and in its kinetic energy?(2)
1. A Momentum doubles; kinetic energy doubles.
2. B Momentum doubles; kinetic energy becomes four times as large.
3. C Momentum becomes four times as large; kinetic energy doubles.
4. D Momentum stays the same; kinetic energy becomes four times as large.
Show the memo (2 ticks)Memo
1. ✓
  Correct option $p = m v$ : $p$ is directly proportional to $v$ , so doubling $v$ doubles $p$ .
  $E_{k} = \frac{1}{2} m v^{2}$ : $E_{k}$ is proportional to $v^{2}$ , so doubling $v$ multiplies $E_{k}$ by $2^{2} = 4$ .
  
  Answer: B
  2 marks · Reason with momentum ratios

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