A crate of weight 15 N lies on a rough slope inclined at an angle of 20∘ 20^\circ\,20∘ to the horizontal. A horizontal force of 12 N acts on the crate and the crate is in equilibrium on the point of slipping up the slope.
Find the coefficient of friction between the crate and the slope.
The 12 N force is removed. Determine whether or not the crate moves.
139 exam-style questions on AQA A Level Maths 3.3 R: Forces and Newton's laws, covering 3.3.1 Concept of a force and Newton's first law, 3.3.2 Newton's second law, 3.3.3 Weight and motion under gravity, 3.3.4 Newton's third law and equilibrium, 3.3.5 Addition of forces and resultants (A-level only), and 3.3.6 Friction (A-level only). Each one has a worked solution and a mark scheme showing where the marks go.