Physics-DPP-1-11.law of motion

PHYSICS Topic: LAWS OF MOTION Date: 1. A mass is hanging on a spring balance which is kept in a lift. The lift ascends with increasing speed. The spring balance will show in its reading : (a) increase (b) decrease (c) no change (d) change will depend upon velocity 2. A monkey is descending from the branch of a tree with a constant acceleration. If the breaking strength of the branch is 75% of the weight of the monkey, the minimum acceleration with which the monkey can slide down without breaking the branck is : 3g (a) g (b) 4 g (c) 2 g (d) 4 3. A body of mass 2 kg is hung on a spring balance mounted vertically in a lift. If the lift moves up with an acceleration equal to the acceleration due to gravity, the reading on the spring balance will be : (a) 2 kg (b) 3 kg (c) 2.5 kg (d) 4 kg 4. The pendulum hanging from the ceiling of a railway carriage makes angle 30o with the vertical, when it is accelerating. The acceleration of the carriage is : (a) 3 g (b) 2 g (c) g (d) g 5. Two bodies of masses 5 kg and 3 kg respectively are connected to two ends of a light spring passing over horizontal frictionless pulley. The tension in the string is : (g = 9.8 m/s2) (a) 60 N (b) 36.75 N (c) 73.50 N (d) 18 N 6. A car having a mass of 1000 kg is moving at a speed of 30 m/s. Brakes are applied to bring the car to rest. If the frictional force between the tyres and the road surface is 5000 N, the car will come to rest in : (a) 5 s (b) 10 s (c) 12 s (d) 6 s 7. Three equal weights A, B and C of mass 2 kg each are hanging on a string passing over a fixed pulley which is frictionless as shown in figure. The tension in the string connecting weight B and C is : (a) zero (b) 13 N (c) 3.3 N (d) 19.6 N 8. Three masses of 6 kg, 4 kg and 2 kg are attached to a rigid support as shown in figure. If the string attached to the support breaks and the system falls freely, then the tension in the string connecting 4 kg and 2 kg mass is : (a) zero (b) 8 kg wt (c) 12 kg wt (d) 6 kg wt 9. If a body loses half of its velocity on penetrating 3 cm in a wooden block, then how much will it penetrate more before coming to rest? (a) 1 cm (b) 2 cm (c) 3 cm (d) 4 cm 10. A ball of mass 0.5 kg moving with a velocity of 2 m/s strikes a wall normally and bounces back with the same speed. If the time of contact between the ball and the wall is 1 millisecond, the average force exerted by the wall on the ball is : (a) 2000 N (b) 1000 N (c) 5000 N (d) 125 N PHYSICS Topic: LAWS OF MOTION Date: Answer Key 1. (a) 2. (d) 3. (d) 4. (d) 5. (b) 6. (d) 7. (b) 8. (a) 9. (a) 10. (a)

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