When work is done on a body by an external force,its

$A$ small block of mass $m$ slides along a smooth track as shown in the figure. If it starts from rest at point $P$,what is the velocity of the block at point $Q$?

$A$ body of mass $5 \ kg$ is placed on a horizontal surface with a coefficient of friction $\mu = 0.2$. It is pulled by a horizontal force of $25 \ N$ for a distance of $10 \ m$. The kinetic energy gained by the body is ..... $J$. (Take $g = 10 \ m/s^2$)

$A$ demonstration apparatus on a table in the lab is shown in the diagram. It consists of a metal track (shown as a thick solid line in the figure) along which a perfectly spherical marble can roll without slipping. In one run,the marble is released from rest at a height $h$ above the table on the left section,rolls down one side and then up the other side without slipping,briefly stopping when it has reached $h_1$. Assuming the table to be horizontal and neglecting air drag as well as any energy loss due to rolling,which of the following is true?

$A$ ball of mass $300 g$ is dropped from a height $10 m$ above a sandy ground. On reaching the ground,it penetrates through a distance $1.5 m$ in sand and finally stops. The average resistance offered by the sand to oppose the motion is (acceleration due to gravity $= 10 m s^{-2}$) (in $N$)

$A$ particle is released from a height $s$. At a certain height,its kinetic energy is three times its potential energy. The height and speed of the particle at that instant are respectively: