General
✓✗The work done by gravity on a body that is moved round a closed path and returns to its starting point is
- negative
- positive
- mgh
- zero
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 child is sitting on a swing. Its minimum and maximum heights from the ground are 0.75 m and 2 m respectively. Its maximum speed will be (take g = 10 m s−2)
- 15 m s−1
- 8 m s−1
- 5 m s−1
- 10 m s−1
General
✓✗A machine does 600 J of work in 2 minutes. Its power is
- 1200 W
- 5 W
- 50 W
- 300 W
General
✓✗A body of mass 4m is lying in the x-y plane at rest. It suddenly explodes into three pieces. Two pieces, each of mass m, move perpendicular to each other with equal speeds v. The total kinetic energy generated due to the explosion is
- 4mv2
- \( \dfrac{3}{2}mv^2 \)
- mv2
- 2mv2
General
✓✗Two bodies of masses 1 kg and 4 kg have equal momenta. The ratio of their kinetic energies is
- 4 : 1
- 1 : 2
- 2 : 1
- 1 : 4
General
✓✗A body moving at constant velocity has its kinetic energy
- increasing
- constant
- decreasing
- zero
General
✓✗A simple pendulum is released from one extreme position. At the lowest point its
- speed is zero
- kinetic energy is zero
- potential energy is maximum
- kinetic energy is maximum
General
✓✗A car of mass 1500 kg has an engine of constant power 60 kW and faces a constant resistance of 2000 N. Its acceleration at a speed of 10 m s−1 is
- \( \dfrac{4}{3} \) m s−2
- 2 m s−2
- \( \dfrac{8}{3} \) m s−2
- 4 m s−2
General
✓✗Statement I: The work done by a force can be negative.
Statement II: The work done by a force depends on the frame of reference.
Statement II: The work done by a force depends on the frame of reference.
- Both Statement I and Statement II are correct
- Both Statement I and Statement II are incorrect
- Statement I is correct but Statement II is incorrect
- Statement I is incorrect but Statement II is correct
General
✓✗A ball of mass 1 kg moving at 4 m s−1 collides with a ball of mass 3 kg at rest and they stick together. The loss of kinetic energy is
- 2 J
- 8 J
- 6 J
- 4 J
General
✓✗The work done by a variable force F(x) is equal to
- F times the final x
- the area under the F-t graph
- the slope of the F-x graph
- the area under the F-x graph
General
✓✗The force corresponding to the potential energy U(x) = 2x2 J is
- 2x3/3 N
- 4x N
- −4x N
- −2x N
General
✓✗The kinetic energy of a body of mass m moving with speed v is
- \( \dfrac12mv^2 \)
- \( \dfrac12mv \)
- mv
- \( mv^2 \)
General
✓✗A 20 g bullet embeds in a 1.98 kg block hanging from a 1 m string. The block swings up until the string makes 60° with the vertical. The speed of the bullet was (g = 10 m s−2)
- 200 m s−1
- 100 m s−1
- \( 10\sqrt{10} \) m s−1
- \( 100\sqrt{10} \) m s−1