Questions on Newton's Laws


The diagram shows an electric two-wheeled vehicle and driver.

(a) The vehicle accelerates horizontally from rest to 27.8 m s–1 in a time of 4.6 s.

The mass of the vehicle is 360 kg and the rider has a mass of 82 kg.

(i) Calculate the average acceleration during the 4.6 s time interval. Give your answer to an appropriate number of significant figures.

[2 marks]

(ii) Calculate the average horizontal resultant force on the vehicle while it is accelerating.

[2 marks]

(b) State and explain how the horizontal forward force on the vehicle has to change for constant acceleration to be maintained from 0 to 27.8 m s–1.

[3 marks]

(c) The electric motors drive both wheels of the vehicle. Add labelled force arrows to diagram of the vehicle to show the horizontal forces acting on the vehicle when it is moving at a constant speed.

[2 marks]

(d) The vehicle now accelerates to a constant speed of 55 m s–1. The useful power output of the motors is 22 kW at this speed.

Calculate the horizontal resistive force acting on the vehicle.

[2 marks]

(11 marks Total)