Once the lorry has reached its destination, the back of the lorry is tilted at an angle 8 to the horizontal.

Three forces act on the box: the weight W, the normal contact force R and the
frictional force F

(i) State expressions for the components of the weight of the box parallel to the back
of the lorry and perpendicular to the back of the lorry.
(2)

W
parallel
W
perpendicular

(ii) The angle is increased until the box is just about to slide.
Given that F= 0.32R, calculate the value of at which the box is just about to slide.

W=200g