Physics-DPP-3-law of motion

PHYSICS Topic: LAWS OF MOTION Date: 1. A light string going over a clamped pulley of mass m supports a block of mass M as shown in the figure. The force of the pulley by the clamp is given by : (a) Mg (b) mg (c) g (d) g 2. In the arrangement shown in figure, there is friction between the blocks of masses m and 2m. The mass of the suspended block is m. The block of mass m is stationary with respect to block of mass 2m. The mimimum value of coefficient of friction between m and 2 m is : 1 (a) 2 (b) 1 1 (c) 4 (d) 3 3. Two masses are connected by a string which passes over a pulley accelerating upwards at a rate as shown. If a1 and a2 be the accelerations of bodies 1 and 2 respectively, then : a2 (a) A = a1 – a2 (b) A = a1 + a2 (c) A = a1 - a2 2 (d) A = a1 + a2 2 4. A block of mass m is placed on a smooth wedge of inclination θ . The whole system is accelerated horizontally so that the block does not slip on the wedge. The force exerted by the wedge on the block has a magnitude : (a) mg tan θ (b) mg sin θ (c) mg cosθ (d) mg secθ PHYSICS Topic: LAWS OF MOTION Date: 5. Block B moves to the right with a constant velocity vo. The velocity of body A relative to B is : (a) vo , towards left 2 (b) (b) vo , towards right 2 (c) 3vo , towards left 2 (d) 3vo , towards right 2 6. A body of mass m rests on horizontal surface. The coefficient of friction between the body and the surface is μ . If the mass is pulled by a force P as shown in the figure, the limiting friction between body and surface will be : é ù é æP öù é æç 3 Pö÷ù (a) μ mg (b) μ êmg – pú (c) μ êmg – ç ÷ú (d) μ êmg – ç ÷ú ê 2 ú ê çè 2 ø÷ú ê ç 2 ÷ú ëê úû ë û ëê è øúû 7. A body takes times t to reach the bottom of an inclined plane of angle θ with the horizontal. If the plane is made rough, time taken now is 2 t. The coefficient of friction of the rough surface is : (a) 3 tan θ 4 (b) 2 tan θ 3 (c) 1 tan θ 4 (d) 1 tan θ 2 8. A block of mass 4 kg is placed on a rough horizontal plane. A time dependent horizontal force F = kt acts on the block, k = 2 N/s2. The frictional force between the block and plane at time t = 2 s is : ( μ= 0.2 ) (a) 4 N (b) 8 N (c) 12 N (d) zero 9. A bead of mass m is located on a parabolic wire as shown in figure and whose eqn is x2 = 2ay. If the coefficient of friction is μ , the highest distance above the x-axis, at which bead will be at rest with respect to frame will be (a) aμ2 μ2a (b) (b) μ2a 2 aμ2 (c) 4 (d) 6 10. Two masses A and B of 10 kg and 5 kg respectively are connected with a string passing over a frictionless pulley fixed at the corner of a table as shown in figure. The coefficient of friction of A with the table is 0.2. The minimum mass of C that may be placed on A to prevent it from moving is equal to : (a) 15 kg (b) 10 kg (c) 5 kg (d) 20 kg PHYSICS Topic: LAWS OF MOTION Date: Answer Key 1. (d) 2. (c) 3. (c) 4. (d) 5. (b) 6. (c) 7. (a) 8. (a) 9. (b) 10. (a)

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