Ben is cycling at 5 mph on a flat road and starts to accelerate to 20 mph. Force A has changed from 14 N to 37 N by the time he reaches 15 mph.
Force B changes from 27 N to 76 N when he starts to accelerate and stays at that value. Force C changes from 13 N to 17 N by the time he reaches 15 mph.

а Suggest which force is the force from the pedals. Explain your answer.

b Work out the resultant horizontal force on the bike at 15 mph and state its direction. Ben continues to pedal with the same force, but his speed stops changing when he reaches 20 mph.

с What is the resultant horizontal force on the bike at 20 mph? Explain your answer.

d How big is the combined force of friction and air resistance at 20 mph? Explain your answer.