Physics-DPP-2-law of motion

PHYSICS Topic: LAWS OF MOTION Date: 1. An elevator and its load have a total mass of 800 kg. If the elevator, originally moving downward at 10 m/s, is brought to rest with constant deceleration in a distance of 25 m, the tension in the supporting cable will be : (g = 10 m/s2) : (a) 8000 N (b) 6400 N (c) 12200 N (d) 9600 N 2. A block of weight 5 N is pushed against a vertical wall by a force 12 N. The coefficient of friction between the wall and block is 0.6. The magnitude of the force exerted by the wall on the block is : (a) 12 N (b) 5 N (c) 7.2 N (d) 13 N 3. The acceleration of the 2 kg block, if the free end of string is pulled with a force of 20 N as shown is : (a) zero (b) 10 m/s2 (c) 5 m/s2 (d) 6 m/s2 4. Two blocks, each having a mass M, rest on frictionless surfaces as shown in the figure. If the pulleys are light and frictionless, and M on the incline is allowed to move down, then the tension in the string will be : (a) 2 Mg sin θ 3 (b) 3 Mgsinθ 2 (c) Mg sin θ 2 (d) 2 Mg sin θ 5. In the shown figure the tension in the upper string immediately after lower string is cut is (a) mg (b) 2 mg (c) 3 mg (d) 3 mg 2 6. In the 5th question the acceleration (in m/s2) of block A & B just after lower string is cut are (a) 0,g ¯ (b) g ­ g ¯ (c) g ¯ g ¯ (d) g ­ g ­ PHYSICS Topic: LAWS OF MOTION Date: 7. A smooth inclined plane of length L, having an inclination θ with horizontal is inside a lift which is moving down with retardation a. The time taken by a block to slide down the inclined plane from rest will be : (a) (b) (c) (d) 8. Three blocks are placed at rest on a smooth inclined plane with force acting on m1 parallel to the inclined plane. Find the contact froce betweem m2 and m3. (a) (m1 + m2 + m3 )F (b) m3F (c) F – (m + m )g (d) None of the above m1 + m2 + m3 1 2 3 9. In this figure how much force on mass m = 5kg should be applied, so that it just won’t slip. Given that car is moving with constant acceleration a = 5 m/s2. (a) 170 N (b) 180 N (c) 150 N (d) 250 N 10. All surfaces shown in figure are smooth. System is released with the spring unstretched. In equilibrium, compression in the spring will be : mg (a) (b) 2mg k (c) (M + m)g mg (d) k PHYSICS Topic: LAWS OF MOTION Date: Answer Key 1. (d) 2. (d) 3. (b) 4. (c) 5. (c) 6. (b) 7. (d) 8. (b) 9. (c) 10. (d)

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