i) If the net force acting on a body is zero, will it remain necessarily at rest?
(ii) Two bodies of mass M and m are allowed to fall from the same height. If air resistance for each body be same, will the two bodies reach the ground simultaneously?

Explanation

(i) No, not necessary. When net force acting on the body is zero, it may be in the state of uniform motion along a straight line.
ii) No. The heavier body will reach the ground earlier. This is because, net downward force on body of mass M = (Mg - F) . Therefore, its acc.,
`a = (Mg - F)/(M) = g - (F)/(M)` and acc. of body of smaller mass, `a = g - (F)/(m)`
As `M gt m :. a gt a`. Hence heavier body will reach the ground earlier than the lighter body.