posted by Jennie .
Joshua has a mass of 60kg and stands next to a wall ona frictionless skateboard. If he pushes the wall with a force of 30N, how hard does the wall push on him? Show that Joshua accelerates at .5 m/s2 away from the wall.
Third law - the wall pushes back with 30N.
F = m a
a = F/m = 30N/60kg = 0.5m/s^2