## Work and Energy MCQs

1. Work done will be zero if the angle between force and displacement is
 A. 30° B. 45° C. 60° D. 90°

1. 30 N force is exerted and the trolley moves a distance of 5 m in the direction of force, the work done is
 A. 6 J B. 25 J C. 150 J D. 0.17 J

1. If the speed of a car decreases by half, the kinetic energy change by factor
 A. 4 B. 2 C. 1/2 D. 1/4

1. An object of mass 10 kg is lifted vertically through a height of 5 m. The gravitational potential energy gained by the object is
 A. 0.5 J B. 2 J C. 50 J D. 490 J

1. If a petrol engine does 20 J of useful work for every 100 J energy supplied to it, then its efficiency is
 A. 80% B. 60% C. 40% D. 20%

1. kWh is unit of
 A. Energy B. Power C. Efficiency D. None

1. 1 hp =
 A. 476 W B. 550 W C. 746 W D. 1 ft.lb/s

1. Hira weighing 500 N takes 90 s to reach the top of a hill 18 m high. Her average muscle power is
 A. 2500 W B. 100 W C. 32.8 W D. 3.24 W

1. A machine is able to lift 200 N of concrete slab vertically up to a height of 30 m above the ground in 50 s. The average power of the machine is
 A. 1.33 W B. 60 W C. 120 W D. 6000 W