Forces, Movement, Shape, and Momentum
4 marks · EasyA student is riding a bicycle. While pedalling, the student applies a forward force of 50 N. The friction and air resistance together produce a resisting force of 20 N.
Calculate the resultant force acting on the bicycle.
The mass of the bicycle and the student is 70 kg. Calculate the acceleration of the bicycle.
Describe one way the student could increase the bicycle's acceleration without changing their mass.
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Show answer
(a) 30 N
(b) 0.43 m/s² m/s^2
(c) Pedal harder to apply a greater forward force.
Common mistakes: Forgetting to subtract the resisting force
Show mark scheme and worked solution
Marking points
M1 (a) · 1 mark · Subtracts resisting force from forward force to find resultant force (50 − 20 = 30 N).
M1 (b) · 1 mark · Uses F = m × a correctly, rearranged to a = F ÷ m. (follow-through)
A1 (b) · 1 mark · Calculates acceleration: 30 N ÷ 70 kg = 0.43 m/s² (accept rounding). (follow-through)
B1 (c) · 1 mark · Describes any method of increasing the force applied (e.g., pedal harder, reduce friction, streamline shape).
Worked solution
To increase the acceleration, the student can pedal harder to generate a larger forward force, or they could reduce the resisting force by making the bicycle more streamlined.