When a body is acted upon by a constant force,then which of the following quantities remains constant?

When $1\,N$ force acts on a $1\,kg$ body that is able to move freely,the body receives:

$A$ ball of mass $0.2 \, kg$ moves with a velocity of $20 \, m/s$ and it stops in $0.1 \, s$; then the force on the ball is ........... $N$.

If the mass and the acceleration of an object are both doubled,how does the force acting on the object change with respect to its previous value?

An army vehicle of mass $1000\, kg$ is moving with a velocity of $10\, m/s$. It is acted upon by a forward force of $1000\, N$ due to the engine and a retarding force of $500\, N$ due to friction. What will be its velocity after $10\, s$ (in $, m/s$)?

The motion of a particle of mass $m$ is described by $y = ut + \frac{1}{2}gt^2$. Find the force acting on the particle.