Work Power Energy

A particle is whirled in a vertical circle of radius $R$. If its velocity at the lowest point is just enough to complete the circle ($u = \sqrt{5gR}$), then the magnitude of its total acceleration when the string…

The spring is initially in an equilibrium condition. Initially it is stretched by length $l$ and the work done is $U_1$. Again, it is stretched by length $\dfrac{7l}{2}$, when the work done is $U_2$, the value of $U_2$…

A ball is thrown vertically downwards from a height of $30$ m with initial velocity $V_0$. It collides with the ground and losses $60\ \%$ of its energy in collision rebounds to $20$ m. The initial velocity $V_0$ is ($g…

A cord is wound round the circumference of wheel of radius r. The axis of the wheel is horizontal and moment of inertia about it is I. A weight mg is attached to the end of the cord and falls from rest. After falling…

The potential energy of a system increases if work is done

A fighter plane is moving in a vertical circle of radius $r$. Its minimum velocity at the highest point $A$ of the circle will be

A metre scale is standing vertically on the earth's surface on one of its end. It now falls on earth without slipping. Find the velocity with which the free end of the scale strikes the earth. $\left(g=10 \mathrm{~m} /…

A block of mass 1 kg slides down a curved track that is one quadrant of a circle of radius 1 m . Speed of the block at the bottom is $2 \mathrm{~m} / \mathrm{s}$. Work done by the frictional force on the block when it…

Simple pendulum of length $l$ has a maximum angular displacement $\theta$. The maximum kinetic energy of the bob is

The work done by all the forces (external and internal) on a system is equal to change in

A body moves a distance of 10 m under the action of force $F=10 \mathrm{~N}$. If the work done is 25 J , the angle which the force makes with the direction of motion is

A running man has half the kinetic energy of that of a boy of half of his mass. The man speed up $1 \mathrm{~m} / \mathrm{s}$, so as the have same kinetic energy as that of a boy. The original speed of the man is