General
✓✗A body of mass 2 kg is dropped from rest. The power of gravity on it 3 s later is (g = 10 m s−2)
- 60 W
- 900 W
- 600 W
- 300 W
General
✓✗A body slides down a smooth incline. Its
- kinetic energy decreases
- total mechanical energy decreases
- potential energy decreases and kinetic energy increases
- potential energy increases
General
✓✗A force F = 3t2 N (t in s) acts on a 1 kg body initially at rest along its line of motion. The work done in the first 2 s is
- 16 J
- 64 J
- 8 J
- 32 J
General
✓✗A ball is dropped from height h on a floor with coefficient of restitution e. The height reached after the second bounce is
- e4h
- eh
- e3h
- e2h
General
✓✗A force F = (5 + 2x) N acts along the x-axis. The work done from x = 1 m to x = 3 m is
- 8 J
- 26 J
- 10 J
- 18 J
General
✓✗A lift of mass 1000 kg moves upward with an acceleration of 1 m s−2. The power delivered by the motor at the instant the speed is 2 m s−1 is (g = 10 m s−2)
- 11 kW
- 20 kW
- 2 kW
- 22 kW
General
✓✗A ball of mass m moving along +x at u collides elastically with an identical ball at rest. After collision both move at angles to the x-axis. The angle between their velocities is
- 45°
- 90°
- 180°
- 60°
General
✓✗A particle moves with a velocity \( (5\hat{i} - 3\hat{j} + 6\hat{k}) \) m s−1 under the action of a constant force \( (10\hat{i} + 10\hat{j} + 20\hat{k}) \) N. The instantaneous power supplied to the particle is
- 200 W
- 100 W
- 140 W
- zero
General
✓✗Water from a dam falls through 100 m at the rate of 103 kg/s and runs a turbine of efficiency 60%. The electrical power produced is (g = 10 m s−2)
- 600 kW
- 400 kW
- 60 kW
- 1 MW
General
✓✗A block of mass 2 kg slides down a 5 m high rough incline from rest and reaches the bottom at 8 m s−1. The heat produced by friction is (g = 10 m s−2)
- 36 J
- 64 J
- 100 J
- 16 J
General
✓✗A 1 kg block is placed gently on the top of a light vertical spring (k = 100 N/m) and released. The maximum compression is (g = 10 m s−2)
- 0.4 m
- 0.1 m
- 0.05 m
- 0.2 m
General
✓✗A particle moves from a point \( (-2\hat{i} + 5\hat{j}) \) to \( (4\hat{j} + 3\hat{k}) \) when a force of \( (4\hat{i} + 3\hat{j}) \) N is applied. How much work has been done by the force?
- 11 J
- 2 J
- 5 J
- 8 J
General
✓✗Which of the following statements about a conservative force is incorrect?
- The work done by it depends on the path
- It can be written as the negative gradient of a potential energy
- The work done by it round a closed path is zero
- Mechanical energy is conserved when only such forces do work
General
✓✗The relation between kinetic energy K and momentum p of a body of mass m is
- \( K = \dfrac{p^2}{2m} \)
- \( K = 2mp^2 \)
- \( K = \dfrac{p}{2m} \)
- \( K = \dfrac{p^2}{m} \)
General
✓✗A shell moving horizontally at speed u at the top of its path explodes into two equal halves. One half retraces its path with speed u. The kinetic energy released in the explosion (shell mass m) is
- mu2
- 2mu2
- 4mu2
- \( \dfrac12mu^2 \)