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Chapter 3 Practice Paper: Dynamics — question paper

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Secondary 3 · Physics (G2 / G3)

Chapter 3 Practice Paper

Dynamics

Duration: 40 minutes
Total: 30 marks
Name:
Class:
Register No.:
Date:

READ THESE INSTRUCTIONS FIRST

  • Write your name, class and register number in the spaces at the top of this page.
  • Answer all questions.
  • Give numerical answers correct to 3 significant figures unless stated otherwise, with units where a quantity is calculated.
  • Take the acceleration of free fall g as 10 m/s² unless stated otherwise.
  • The number of marks is given in brackets [ ] at the end of each question or part question.
  • The total number of marks for this paper is 30.

Original practice material written for the MOE Physics syllabus. It is not an official MOE or school examination paper. Forces, mass and weight, Newton’s laws, free-body diagrams, friction and terminal velocity.

For Examiner’s Use
Section A/ 10
Section B/ 20
Total/ 30

Section A: Multiple-choice questions[10 marks]

Choose the one correct answer for each question.

  1. 1

    Which force is a non-contact force?

    1. Afriction between a box and a ramp
    2. Bthe magnetic pull on a steel door
    3. Ctension in a tow rope
    4. Dthe normal force from a floor
    ( )
  2. 2

    The weight of a 60 kg adult, taking g = 10 N/kg, is

    1. A6.0 N
    2. B60 N
    3. C600 N
    4. D6000 N
    ( )
  3. 3

    A trolley of mass 2.0 kg is pushed along a bench with 8.0 N while friction acts with 2.0 N. Its acceleration is

    1. A3.0 m/s²
    2. B2.0 m/s²
    3. C4.0 m/s²
    4. D5.0 m/s²
    ( )
  4. 4

    A book rests on a table. Which pair is a Newton’s-third-law action–reaction pair?

    1. Athe weight of the book and the normal force from the table
    2. Bthe weight of the book and the pull of the Earth on the Sun
    3. Cthe push of the book on the table and the weight of the table
    4. Dthe normal force from the table and the push of the book on the table
    ( )
  5. 5

    A skydiver falls at constant speed with her parachute open. The resultant force on her is

    1. Adownwards and equal to her weight
    2. Bzero
    3. Cupwards and larger than her weight
    4. Dupwards and equal to her weight
    ( )

Section B: Structured questions[20 marks]

Answer all questions in the spaces provided.

  1. 1

    A crate of mass 18 kg sits on a rough floor. A worker pushes it horizontally with 90 N and friction opposes with 54 N.

    1. (a)

      Calculate the weight of the crate.

      weight =N[1]
    2. (b)

      Calculate the resultant horizontal force on the crate.

      resultant =N[1]
    3. (c)

      Calculate the acceleration of the crate.

      acceleration =m/s²[2]
    4. (d)

      The worker now pushes with 54 N. Describe the motion of the crate and explain your answer.

      [2]
  2. 2

    A skydiver of mass 70 kg jumps from a plane. Ignore horizontal motion throughout. Take g = 10 m/s².

    1. (a)

      State the value of her weight.

      weight =N[1]
    2. (b)

      At one moment the drag on her is 250 N. Calculate her resultant force and acceleration at that moment.

      acceleration =m/s²[3]
    3. (c)

      Explain, using forces, why she eventually falls at a constant terminal speed before opening the parachute.

      [2]
    4. (d)

      Just after the parachute opens, the drag is 1500 N. Calculate her acceleration and state its direction.

      acceleration =m/s²[2]
  3. 3

    A lift of mass 250 kg carries one passenger of mass 60 kg. The lift cable pulls upwards with a total tension T. Take g = 10 m/s².

    1. (a)

      Calculate the total weight of lift plus passenger.

      weight =N[1]
    2. (b)

      The lift accelerates upwards at 1.5 m/s². Calculate the tension T.

      T =N[3]
    3. (c)

      The lift now moves upwards at constant speed. State the new tension with a reason.

      T =N[2]

— End of paper —