Work, energy and the conservation of energyEdexcel A-Level Physics: Subtopic test

1. 1
   A traveller pulls a suitcase 20 m along a level airport floor using a handle. The handle is held at 30° above the horizontal and the pulling force is a constant 60 N. The suitcase moves at a constant speed.

   (a)

   Calculate the work done by the pulling force on the suitcase.

   [1 mark]

   • A600 J
   • B1200 J
   • C1390 J
   • D1040 J

   (b)

   Which statement about the energy transfers for the suitcase is correct?

   [1 mark]

   • AThe work done is stored as kinetic energy of the suitcase
   • BThe work done by the pulling force is zero because the floor is level
   • CThe work done by the pull is transferred as thermal energy by friction, and the kinetic energy is unchanged
   • DThe work done increases the gravitational potential energy of the suitcase by 1040 J

   (c)

   Calculate the frictional force acting on the suitcase.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   A child releases a toy car of mass 0.30 kg from rest at the top of a straight ramp. The top of the ramp is 0.80 m above the floor. Take g = 9.81 N kg⁻¹.

   (a)

   Calculate the gravitational potential energy lost by the car as it moves from the top of the ramp to the floor.

   [1 mark]

   • A2.4 J
   • B0.24 J
   • C7.9 J
   • D1.2 J

   (b)

   The ramp is smooth and air resistance is negligible. What is the speed of the car at the bottom of the ramp?

   [1 mark]

   • A2.8 m s⁻¹
   • B4.0 m s⁻¹
   • C7.9 m s⁻¹
   • D16 m s⁻¹

   (c)

   In practice the car reaches the bottom of the ramp at 3.2 m s⁻¹. Calculate the energy transferred to the surroundings as thermal energy.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   A skier of mass 70 kg starts from rest at the top of a straight slope and skis down to the bottom. The bottom of the slope is 45 m lower than the top and the slope is 280 m long. At the bottom the skier's speed is 22 m s⁻¹. Take g = 9.81 N kg⁻¹.

   (a)

   Calculate the gravitational potential energy lost by the skier, the kinetic energy gained, and the energy dissipated as thermal energy.

   [3 marks]

   (b)

   Calculate the average resistive force on the skier. Explain why the resistive force at the bottom of the slope is likely to be greater than this average.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   A fairground trolley of mass 450 kg, including its passengers, is released from rest at point A on a track. A is 30 m above the lowest point of the track. After the lowest point the track rises over a second hill whose top is 24 m above the lowest point. Take g = 9.81 N kg⁻¹.

   (a)

   Describe and explain the energy transfers as the trolley moves from A to the top of the second hill. Explain how conservation of energy applies when resistive forces are, and are not, included.

   [6 marks]

   (b)

   The track length from A to the top of the second hill is 150 m. The speed of the trolley at the top of the second hill is measured as 6.0 m s⁻¹. Calculate the average resistive force on the trolley, and explain why this value is only an average.

   [6 marks]

   Total for question 4: 12 marks

End of questions