If a body is in motion,is it necessary that it is being acted upon by a force?

Which would require a greater force $-$ accelerating a $2 \ kg$ mass at $5 \ m s^{-2}$ or a $5 \ kg$ mass at $3 \ m s^{-2}$?

$A$ water sprinkler used for grass lawns begins to rotate as soon as the water is supplied. Explain the principle on which it works.

$A$ water tanker filled up to $2/3$ of its height is moving with a uniform speed. On sudden application of the brake,the water in the tank would

Name the physical quantity that measures inertia. State its $SI$ unit.

Give the magnitude and direction of the net force acting on:
$(a)$ a drop of rain falling down with a constant speed.
$(b)$ a cork of mass $10 \,g$ floating on water.
$(c)$ a kite skilfully held stationary in the sky.