WA2 Practice Paper: Forces, Dynamics and Moments — question paper

Section A: Multiple-choice questions[10 marks]

Answer all questions. For each question, write the letter (A, B, C or D) of the correct answer.

1. 1

   An astronaut has a mass of 70 kg. On the Moon (gravitational field strength 1.6 N/kg) her weight is

   1. A70 N
   2. B112 N
   3. C700 N
   4. D43.75 N
   ( )
2. 2

   A metal block has mass 240 g and volume 80 cm³. Its density is

   1. A0.33 g/cm³
   2. B3.0 g/cm³
   3. C19200 g/cm³
   4. D320 g/cm³
   ( )
3. 3

   A crate weighing 300 N stands on a floor area of 1.5 m². The pressure it exerts is

   1. A450 Pa
   2. B200 Pa
   3. C300 Pa
   4. D0.005 Pa
   ( )
4. 4

   A resultant force of 12 N acts on a 4.0 kg trolley. Its acceleration is

   1. A3.0 m/s²
   2. B48 m/s²
   3. C0.33 m/s²
   4. D16 m/s²
   ( )
5. 5

   A box slides across a rough floor, slowing down. The force slowing it down is

   1. Aits weight
   2. Bthe normal contact force
   3. Cfriction
   4. Dits inertia
   ( )
6. 6

   A book rests on a table. The reaction force of the table on the book is the Newton’s-third-law partner of

   1. Athe book’s weight
   2. Bthe book pressing on the table
   3. Cthe friction on the book
   4. Dthe table’s weight
   ( )
7. 7

   A force of 20 N acts 0.50 m from a pivot, perpendicular to the lever. The moment is

   1. A40 N m
   2. B0.025 N m
   3. C10 N m
   4. D20.5 N m
   ( )
8. 8

   A seesaw balances when the clockwise moments equal

   1. Athe total weight
   2. Bthe anticlockwise moments
   3. Cthe number of children
   4. Dthe largest single moment
   ( )
9. 9

   A uniform metre rule balances on a knife-edge at the

   1. A0 cm mark
   2. B100 cm mark
   3. C50 cm mark
   4. D25 cm mark
   ( )
10. 10

    A car moves at constant velocity along a road. The resultant force on the car is

    1. Aforward and large
    2. Bzero
    3. Cbackwards
    4. Dequal to its weight
    ( )

Section B: Structured questions[30 marks]

Answer all questions in the spaces provided. Show all necessary working. Take g = 10 m/s².

1. 1

   A metal block has mass 240 g and volume 80 cm³. It rests on a tabletop on a face of area 0.020 m².

   1. (a)

      Calculate the density of the block, in g/cm³.

      density =g/cm³[2]
   2. (b)

      Calculate the weight of the block, in newtons.

      weight =N[2]
   3. (c)

      Calculate the pressure the block exerts on the table.

      pressure =Pa[3]
2. 2

   A student pulls a 2.0 kg trolley along a rough floor with a horizontal force of 10 N. A frictional force of 2.0 N opposes the motion.

   1. (a)

      Calculate the resultant force on the trolley.

      resultant =N[2]
   2. (b)

      Calculate the trolley’s acceleration.

      a =m/s²[2]
   3. (c)

      The student now pulls so the trolley moves at constant velocity. State the size of the pulling force and the resultant force, with a reason.

      [3]
3. 3

   A uniform metre rule is pivoted at its centre (the 50 cm mark). A 4.0 N weight hangs from the 30 cm mark.

   1. (a)

      Calculate the anticlockwise moment of the 4.0 N weight.

      moment =N m[2]
   2. (b)

      Calculate where a 3.0 N weight must hang on the right to balance the rule, and state the rule reading.

      distance =m[3]
   3. (c)

      State why the rule’s own weight does not appear in the calculation.

      [1]
   4. (d)

      State the principle of moments.

      [2]
4. 4

   An astronaut’s mass is 60 kg. The Moon’s gravitational field strength is 1.6 N/kg; the Earth’s is 10 N/kg.

   1. (a)

      Calculate the astronaut’s weight on Earth and on the Moon.

      weights =N[2]
   2. (b)

      State the astronaut’s mass on the Moon, with a reason.

      [2]
   3. (c)

      The astronaut jumps and leaves the ground at 3.0 m/s. Calculate her maximum height gain on the Moon, where the deceleration is 1.6 m/s².

      height =m[4]