ok the problem goes like this:
Mass mA rests on a smooth horizontal surface, mB hangs vertically.
1 . If mA=13.0 kg and mB =3.0 kg , determine the magnitude of the acceleration of each block.
2 . If initially mA is at rest 1.150m from the edge of the table, how long does it take to reach the edge of the table if the system is allowed to move freely?
3 . If mB=1.0kg, how large must mA be if the acceleration of the system is to be kept at 1/100 g?
F = mg = 3g
F = ma ==> a = F/m = 3g/16 = 1.84 m/s2 (Answer 1)
s = 1/2 at^2 ==> t^2 = 2s/a = 2.30 / (3g/16) = 4.23 ==> t = 2.06 sec. (Answer 2)
F = g
a = F/m = g/100 = g/(m+1) ==> m + 1 = 100 ==> m = 99 kg (Answer 3)