Potential energy of an object at a height $h$ is $E_p=mgh$. This equation is true only if

(i) The acceleration due to gravity is constant.
(ii) The potential energy is path dependent.

A skier of mass $50 \mathrm{kg}$ stands at point $P$ at the top of the ski jump and moves from $P$ to $Q$ and takes off his jump at $Q$ as shown in figure. If $50\%$ of the change in the gravitational potential energy of the skier between points $P$ and $Q$ becomes the kinetic energy at $Q$ then the speed at which the skier arrives at $Q$ is:

(Take, $g=10 \raisebox{1ex}{$\mathrm{m}$}\!\left/ \!\raisebox{-1ex}{${\mathrm{s}}^2$}\right.$)

A body moves under a variable force. For the body a plot of velocity versus time is shown in figure. The correct statement is:

Two inclined frictionless tracks, one gradual and the steep meet at point $A$ from where two stones (I and II) are allowed to slide down from rest, one on each track as shown in figure. Which one of the following statements is correct?

The diagram shows a cyclist moving down a small hill at $P$ before travelling on a flat road at $Q$. The total mass of the cyclist and his bicycle is $60 \mathrm{kg}$ and the speed of the cyclist at $P$ is $10 {\mathrm{ms}}^{-1}$. Which of the following is incorrect?