The work done by the external forces on a system equals the change in:
1. total energy
2. kinetic energy
3. potential energy
4. none of these

A small block of mass \(m\) is kept on a rough inclined surface of inclination \(\theta\) fixed in an elevator. The elevator goes up with a uniform velocity \(v\) and the block does not slide on the wedge. The work done by the force of friction on the block in time \(t\) will be:
1. zero
2. \(mgvt ~cos^2\theta\)
3. \(mgvt ~sin^2\theta\)
4. \(mgvt ~sin2\theta\)

A block of mass \(m\) slides down a smooth vertical circular track. During the motion, the block is in:
1. vertical equilibrium
2. horizontal equilibrium
3. radial equilibrium
4. none of these

A particle is acted upon by a force of constant magnitude which is always perpendicular to the velocity of the particle. The motion of the particle takes place in a plane. It follows that:

Choose the correct option from the options given below:

Consider two observers moving with respect to each other at a speed v along a straight line. They observe a block of mass m moving a distance I on a rough surface. The following quantities will be same as observed by the two observers

1. kinetic energy of the block at time t

2. work done by friction

3. total work done on the block

4. acceleration of the block

No work is done by a force on an object if:

Choose the correct option: