Title 1. Low of motion (Sub.Q ) E.pdf ✅

PHYSICS Q.1 A body of mass 45 kg. is moving with a constant velocity of 10 m/s. A constant force acts on the body for four second, and the speed of the body becomes 2 m/s in opposite direction, calculate the acceleration produced. Ans. – 3 m/s2 Q.2 Two blocks A and B of masses m1 and m2 respectively are in contact on frictionless horizontal table. A horizontal force is applied to the block A as shown in the figure. Take m1 = 3 kg , m2 = 2 kg and F = 5 N. F m1 A B m2 (A) Find the force of contact between the two blocks. (B) Show that it the same force F = 5 N is applied to m2 rather than m1 then the force of contact between the two blocks will have a different value. Ans. 2 N Q.3 The two blocks shown in figure are connected by a heavy uniform rope of mass 4 kg. An upward force of 200 N is applied as shown in figure. F 7 kg 4 kg 5 kg (a) What is the acceleration of the system ? (b) What is the tension at the top of the heavy rope? Ans. (a) 2.69 m/s2 upward (b) 112.5 N (c) 87.5 N Q.4 At the moment t = 0, a stationary particle of mass m experiences a time-dependent force F = k t (t' - t), where k is a constant vector, t' is the time during which the given force acts. Find- (a) the momentum of the particle when the action of the force discontinued; (b) the distance covered by the particle while the force acted. Ans. (a) k(t')3 /6 (b) k(t')4 /12 m Q.5 A uniform flexible chain of length l, with weight per unit length , passes over a small frictionless mass less pulley. It is released from a rest position with a length of chain x hanging from one side and a length (l – x) from the other side. (a) Under what circumstances will it accelerate? (b) Assuming these circumstances are met, find the acceleration a as a function of x. Ans. (a) x =  / 2; (b) a = g (1–  2x ) Q.6 A 10 kg monkey is climbing a mass less rope attached to a 15 kg mass over a (frictionless!) tree limb. (a) Explain quantitatively how the monkey can climb up the rope so that he can raise the 15 kg mass off the ground. (b) If, after the mass has been raised off the ground, the monkey stops climbing and holds on to the rope, what will his acceleration and the tension in the rope now be ? Ans. (a) a  g/2 ; (b) a = g/5, T = 118 N Q.7 A block is kept on the floor of an elevator at rest. The elevator starts descending with an acceleration of 12 m/s2. Find the displacement of the block during the first 0.2 s after the start. Take g = 10 m/s2. Ans. 20 cm