A cyclist is towing a trailer behind her bicycle - AQA - A-Level Maths Pure - Question 15 - 2021 - Paper 2

To find the tension $T$, we can analyze the forces acting on the trailer. Since the cyclist is moving at a constant speed, the forces acting on the trailer must be balanced. The force exerted by the cyclist is 40 N in the forward direction, while the resistance force acting against the trailer is 12 N.

Using the equilibrium condition:

$F_{net} = F_{driving} - F_{resistance} - T = 0$

This implies:

$40 ext{ N} - 12 ext{ N} - T = 0$

Thus, rearranging gives:

$T = 40 ext{ N} - 12 ext{ N} = 28 ext{ N}$

However, since the tension $T$ must also balance this resistance, the correct value for $T$ in equilibrium is:

$T = 12 ext{ N}$