When a net force acts on an object,the object will be accelerated in the direction of the force with an acceleration proportional to:

While riding a bicycle,if we stop pedalling,why does the bicycle begin to slow down?

$A$ truck starts from rest and rolls down a hill with constant acceleration. It travels a distance of $400 \, m$ in $20 \, s$. Find its acceleration. Find the force acting on it, if its mass is $7$ metric tons.

Inertia is that property of a body by virtue of which the body is

$(a)$ State Newton's second law of motion. Use this law to find a method to measure force acting on an object.
$(b)$ From a rifle of mass $4 \ kg$,a bullet of mass $50 \ g$ is fired horizontally with an initial velocity of $40 \ m \ s^{-1}$. Calculate the initial recoil velocity of the rifle.

Kicking a football requires less force than kicking a basketball. Why?