$A$ book of mass $5 \,kg$ is placed on a table and it is pressed by $10 \,N$ force. Then,the normal force exerted by the table on the book is ......... $N$.

$A$ stone of mass $0.05 \,kg$ is thrown vertically upwards. What is the direction and magnitude of the net force on the stone during its upward motion?

$A$ man of mass $50 \,kg$ carries a bag of weight $40 \,N$ on his shoulder. The force with which the floor pushes up his feet will be ......... $N$.

$P, Q$ and $R$ are three coplanar forces acting at a point and are in equilibrium. Given $P = 1.9318 \, kg \, wt$,$\sin {\theta _1} = 0.9659$,the value of $R$ is (in $kg \, wt$):

$A$ spherical ball of mass $m=5\,kg$ rests between two planes which make angles of $30^{\circ}$ and $45^{\circ}$ respectively with the horizontal. The system is in equilibrium. Find the normal forces exerted on the ball by each of the planes. The planes are smooth.

Define mechanical advantage in a lever.