Physics-DPP-2-work, power and energy

PHYSICS Topic: WORK, POWER AND ENERGY Date: 1. Power applied to a particle varies with time as P = (3t 2 - between time t = 2s and t = 4 s. 2t + 1)W , where t is in second. Find the change in its kinetic energy (a) 32 J (b) 46 J (c) 61 J (d) 102 J 2. A body moves from rest with a constant acceleration. Which one of the following graphs represents the variation of its kinetic energy K with the distance travelled x ? (a) (b) (c) (d) g 3. A mass M is lowered with the help of a string by a distance x at a constant acceleration 2 . The magnitude of work done by the string will be : (a) Mgx (b) 1 Mgx2 2 (c) 1 Mgx (d) Mgx2 2 4. A particle of mass 0.01 kg travels with velocity given by 4iˆ + 16kˆ ms–1 . After sometime, its velocity becomes 8iˆ + work done on particle during this interval of time is : (a) 0.32 J (b) 6.9 J (c) 9.6 J (d) 0.96 J 20 ˆj ms–1 . The 5. A bead can slide on a smooth circular wire frame of radius r which is fixed in a verticle plane. The bead is displaced slightly from the highest point of the wire frame. The speed of the bead subsequently as a function of the angle θ made by the bead with the vertical line is : (a) (d) 2 6. A particle moves in a straight line with retardation proportional to its displacement. Its loss of kinetic energy for any displacement x is proportional to : (a) x (b) x2 (c) ln x (d) ex 7. A block of mass m is pulled along a horizontal surface by applying a force at an angle θ with the horizontal. If the block travels with a uniform velocity and has a displacement d and the coefficient of friction is μ , the work done by the applied force is : μmgd (a) cosθ + μ sin θ (b) (b) μmgd cosθ cosθ + μ sin θ (c) (c) μmgd sin θ cosθ + μ sin θ (d) (d) μmgd cosθ cosθ – μ sin θ PHYSICS Topic: WORK, POWER AND ENERGY Date: 8. Work done in time t on a body of mass m which is accelerated from rest to a speed v in time t1, as a function of time t is given by : æ1ö æçv ö÷ 2 æv ö æ1 öæmvö2 æ1ö æçv2 ö÷ (a) ç ÷mç ÷t (b) mç ÷t 2 (c) ç ÷ç ÷ t (d) ç ÷mç ÷t2 2ø÷ çèt1 ø÷ çt ÷ çè2÷øçè t ÷ çè2ø÷ çt 2 ÷ è 1 ø 1 ø è 1 ø 9. A force F acting on a body depends on its displacement S as F µ S–1/3 . The power delivered by F will depend on displacement as : (a) S2/3 (b) S –5/3 (c) S1/2 (d) S0 10. If v be the instantaneous velocity of the body dropped from the top of a tower, when it is located at height h, then which of the following remains constant ? (a) gh + v2 (b) v2 gh + 2 (c) v2 gh - 2 (d) gh - v2 PHYSICS Topic: WORK, POWER AND ENERGY Date: Answer Key 1. (b) 2. (c) 3. (c) 4. (d) 5. (c) 6. (b) 7. (b) 8. (d) 9. (d) 10. (b)

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