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 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 body of mass \(1\) kg is thrown upwards with a velocity \(20\) ms-1. It momentarily comes to rest after attaining a height of \(18\) m. How much energy is lost due to air friction?
(Take \(g=10\) ms-2)
1. \(20\) J
2. \(30\) J
3. \(40\) J
4. \(10\) J
In a ballistics demonstration, a police officer fires a bullet of mass \(50.0\) g with speed \(200\) m/s on soft plywood of thickness \(2.00\) cm. The bullet emerges with only \(\text{10%}\) of its initial kinetic energy. The emergent speed of the bullet is:
1. | \(0\) | 2. | \(53.2\) m/s |
3. | \(63.2\) m/s | 4. | \(6.32\) m/s |