Answer:
M.A = load/ effort
1200N/400N
= 3
velocity ratio= radius of wheel/radius of Axle
40cm/10cm
=4
efficiency= 3/4*100
75%
If a man pushes on a wall with some force then according to Newton's third law, wall will also apply force on man with same magnitude but opposite in direction.
Hello!

Use the equation for momentum:

Plug in the given mass and velocity into the equation:

