What causes objects to move or stay still?

If it is still, it will tend to remain still, due to inertia. But a net force would start it moving. 
If it is moving, it will tend to continue moving, due to inertia. But a net force, in the right direction, could cause it to stop. But if that force continues, it will start moving in the opposite direction.

Hope this helps  :)

    5.5 n======    assuming that      we have      m = 0.145 kg    a = 38 m/s²therefore    5.51 n, but two significant figures.final answer: 5.5 n

P