The work done by all the forces (external and internal) on a system equals the change in:
1. total energy
2. kinetic energy
3. potential energy
4. none of these
A block of \(1\) kg is released from the top of a smooth curve \(\mathrm{AB},\) and then it encounters a rough surface \(\mathrm{BC},\) coming to rest at \(\mathrm{C}.\) The work done by friction is:
(take \(g=10\) m/s2)
1. | \(25\) J | 2. | \(50\) J |
3. | \(-25\) J | 4. | \(-50\) J |
The minimum speed that a simple pendulum's bob should be given so that it rises to a level where its string makes \(60^\circ\) with the vertical is:
1. | zero | 2. | \(-\dfrac12mu^2\cos^2\theta\) |
3. | \(-\dfrac12mu^2\sin^2\theta\) | 4. | \(-\dfrac12mu^2\) |