## Work and Energy MCQs

Choose the best possible answer.

- Work done will be zero if the angle between force and displacement is

A. 30° | B. 45° | C. 60° | D. |

- 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. | D. 0.17 J |

- If the speed of a car decreases by half, the kinetic energy change by factor

A. 4 | B. 2 | C. 1/2 | D. |

- 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. |

- 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. |

- kWh is unit of

A. | B. Power | C. Efficiency | D. None |

- 1 hp =

A. 476 W | B. 550 W | C. | D. 1 ft.lb/s |

- 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. | C. 32.8 W | D. 3.24 W |

- 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. | D. 6000 W |