Sumit does 600 J of work in 10 min and Amit does 300 J of work in 20 min. Calculate the ratio of the powers delivered by them.

Two identical marbles A and B are rolled down along Path 1 and Path 2 respectively. Path 1 is frictionless and Path 2 is rough. (a) Which marble will surely reach the next peak? (b) Along which path/s the mechanical energy will be conserved? (c) Along which path/s is the law of conservation of energy obeyed?

When the speed of a moving object is doubled, then its kinetic energy: (a) remains the same (b) decreases (c) is doubled (d) becomes four times

The energy conversion in a washing machine is from ............... (a) magnetic to electrical (b) electrical to mechanical (c) electrical to magnetic (d) magnetic to electrical

What is the correct energy transformation during burning of a candle? (a) heat → kinetic + potential (b) heat → chemical + light (c) chemical → heat + light (d) mechanical → chemical + heat

The energy transformation that takes place during photosynthesis is: (a) heat energy to chemical energy (b) chemical energy to light energy (c) light energy to chemical energy (d) chemical energy to heat energy

A cyclist stops pedalling while moving along a frictionless hilly road. Which quantity remains constant? (a) Kinetic energy (b) Potential energy (c) Total mechanical energy increases (d) Total mechanical energy remains constant

A car of mass 120 kg is moving at a speed 18 km/h and it accelerates to attain a speed of 54 km/h in 5 seconds. Calculate: (a) the work done by the engine. (b) the power of the engine.

Calculate the power spent by a crane while lifting a load of mass 2000 kg, at velocity of 1.5 m s−1. (g = 10 m s−2).

(a) What should be the angle between the direction of force and the direction of displacement, for work to be negative? (b) Name the physical quantity obtained using the formula , where U is the potential energy and h is the height.

Richa weighing 40 kgf leaves point P on her skateboard and reaches point Q on the ground with velocity 10 m s⁻¹. Calculate: (a) the kinetic energy of Richa at point Q (b) the vertical height of point P above the ground. (Use g as 10 m s⁻² and neglect friction.) (c) the kinetic energy of Richa at point R. (While moving from Q to R, she loses 500 J of energy against friction.)

A ball of mass 20 g falls from a height of 45 m. It rebounds from the ground to a height of 40 m. Calculate: (a) initial potential energy of the ball. (b) the speed of the ball at which it hits the ground. (c) the loss in kinetic energy on striking the ground. [g = 10 m s−2]