Hi again, got more assistance requirements again. BTW, last time MR helped me with maths I got 96% for the exam- the highest in the grade. So... A toy cannon (0.4kg) is at rest. The cannon shots a ball (0.025kg). Immediately after firing the shot the cannon rolls back at 0.2m.s-1, then comes to rest. 1. Calculate teh magnitude of the velocity of the ball. (I got 3.2m.s-1) 2. If the acceleration of the cannon is 0.05m.s-2 calculate the magnitude of the frictional force of the ground on teh cannon. so far I have got F=m.a=Fball - Ffriction =0.4 * 0.05 =Fb-Ff At this point I cant get Fb since no time is given.