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:
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
| 1. | \(\sqrt{\dfrac{k}{m}}x\) | 2. | \(\sqrt{\dfrac{m}{k}}x\) |
| 3. | \(\sqrt{\dfrac{k}{m}}(2x)\) | 4. | \(\sqrt{\dfrac{k}{m}}\left(\dfrac{x}{2}\right)\) |

| 1. | zero | 2. | \(-\dfrac12mu^2\cos^2\theta\) |
| 3. | \(-\dfrac12mu^2\sin^2\theta\) | 4. | \(-\dfrac12mu^2\) |