FrictionEdexcel A-Level Maths: Mind map

Exam questions on Friction

1. A box of mass 10 kg rests on a rough horizontal floor. The coefficient of friction between the box and the floor is 0.3. A horizontal force is applied to the box. Take $g=9.8\ \text{m s}^{-2}$.
   Explain why the friction force in part (a) is 25 N and not $\mu R$, and state the greatest horizontal force that can be applied without the box moving.2 marks
2. A particle of mass 5 kg is placed on a rough plane inclined at $20^\circ$ to the horizontal. The coefficient of friction between the particle and the plane is $\mu$. Take $g=9.8\ \text{m s}^{-2}$.
   The coefficient of friction is now 0.3 and the particle slides down the plane. Find its acceleration.2 marks
3. A crate of mass 20 kg is pulled along a rough horizontal floor by a light rope inclined at $30^\circ$ above the horizontal. The tension in the rope is 80 N, the crate is moving and the coefficient of friction between the crate and the floor is 0.25. Take $g=9.8\ \text{m s}^{-2}$.
   Find the magnitude of the normal reaction of the floor on the crate and the magnitude of the friction force.3 marks