Mountain roads rarely go straight up but wind up gradually. Why?

What happens to the kinetic energy when
$(i)$ the mass of the body is doubled at constant velocity?
$(ii)$ the velocity of the body is doubled at constant mass?
$(iii)$ the mass of the body is doubled but the velocity is reduced to half?

$A$ man weighing $70 \,kg$ carries a weight of $10 \,kg$ to the top of a tower $100 \,m$ high. Calculate the work done.

$(a)$ How much work is done when a force of $1\, N$ moves a body through a distance of $1\, m$ in its direction?
$(b)$ Is it possible that a force is acting on a body but still the work done is zero? Explain giving one example.

$A$ body moves along a circular path. How much work is done in doing so? Explain.

The velocity of a body moving in a straight line is increased by applying a constant force $F$, for some distance in the direction of the motion. Prove that the increase in the kinetic energy of the body is equal to the work done by the force on the body.