1. 1
   A removals worker pushes a box a distance of 8 m across a warehouse floor, applying a steady horizontal force of 40 N in the direction of motion.

   (a)

   How much work is done on the box?

   [1 mark]

   • A320 J
   • B48 J
   • C5 J
   • D0.2 J

   (b)

   What is the unit in which the work done on the box is measured?

   [1 mark]

   • AThe watt
   • BThe newton
   • CThe joule
   • DThe metre

   (c)

   Explain the relationship between the work done on the box and the energy transferred to it as it moves across the floor.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   A weightlifter raises a barbell of weight 900 N through a vertical height of 2.0 m, then holds it stationary above her head for several seconds.

   (a)

   How much work does the weightlifter do in lifting the barbell?

   [1 mark]

   • A1800 J
   • B902 J
   • C450 J
   • D1.8 J

   (b)

   Into which energy store is the work done by the weightlifter mainly transferred as she raises the barbell?

   [1 mark]

   • AThe chemical energy store of the barbell
   • BThe nuclear energy store of the barbell
   • CThe electrostatic energy store of the barbell
   • DThe gravitational potential energy store of the barbell

   (c)

   Once the barbell is raised, the weightlifter holds it stationary above her head for several seconds. Explain why no further work is being done on the barbell during this time, even though the weightlifter's muscles are exerting a large force to support it.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   A tractor pulls a loaded trailer a distance of 150 m across a field, exerting a steady pulling force of 3000 N. Separately, an electric fan is switched on and its blades begin to rotate, pushing air outwards.

   (a)

   Calculate the work done by the tractor on the trailer, and state what this work done is equal to.

   [3 marks]

   (b)

   An electric fan is switched on, and electrical work is done on the fan's motor, causing the blades to rotate. Explain what is meant by electrical work done in this context, and describe the energy transfers that take place from the electrical work done on the motor to the final energy stores affected.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   A warehouse uses a motor-driven conveyor belt to lift boxes up a ramp, and also uses an electric heater to keep a small office warm.

   (a)

   A motor-driven conveyor belt in a warehouse lifts boxes up a straight ramp. Describe how the equation W = Fd = ΔE applies to a box of weight 150 N being lifted a distance of 6 m along the ramp by a steady pulling force of 90 N (acting along the ramp), explaining what happens to the energy transferred, and calculate the work done by the motor on the box.

   [6 marks]

   (b)

   Explain the general principle that both mechanical work done and electrical work done are equal to the amount of energy transferred, comparing the conveyor belt (doing mechanical work on a box) with an electric heater (doing electrical work to warm a room), and discuss why not all of the work done by the conveyor belt's motor ends up as useful energy transferred to the boxes.

   [6 marks]

   Total for question 4: 12 marks

End of questions