Physics-DPP-1-3.CENTRE OF MASS, CONSERVATION OF MOMENTUM, COLLISION

PHYSICS Topic: CENTRE OF MASS, CONSERVATION OF MOMENTUM, COLLISION Date: 1. A bullet of mass 5 g is fired at a velocity 900 ms–1 from a rifle of mass 2.5 kg. What is the recoil velocity of the rifle? (a) 0.9 ms–1 (b) 180 ms–1 (c) 900 ms–1 (d) 1.8 ms–1 2. A stationary bomb explodes into two parts of masses 3 kg and 1 kg. The total KE of the two parts after explosion is 2400 J. The KE of the smaller part is : (a) 600 J (b) 1800 J (c) 1200 J (d) 2160 J 3. One projectile moving with velocity v in space, gets burst into 2 parts of masses in the ratio 1 : 3. The smaller part becomes stationary. What is the velocity of the other part? 4v (a) 4 v (b) v (c) 3 3v (d) 4 4. A uniform square plate ABCD has a mass of 10 kg. If two points masses of 5 kg each are placed at the corners C and D as shown in the adjoining figure, then the center of mass shifts to the mid-point of : (a) OH (b) DH (c) OG (d) OF 5. Two particles A and B initially at rest, move towards each other under a mutual force of attraction. At the instant when the speed of A is v and the speed of B is 2v, the speed of centre of mass of the system is : (a) zero (b) v (c) 1.5 v (d) 3 v 6. A circular plate of diameter d is kept in contact with a square plate of edge d as shown in figure. The density of the material and the thickness are same everywhere. The centre of mass of the composite system will be : (a) inside the circular plate (b) inside the square plate (c) at the point of contact (d) outside the system 7. Two blocks of masses 10 kg and 4 kg are connected by a spring of negligible mass and placed on a frictionless horizontal surface. An impulse gives a velocity of 14 m/s to the heavier block in the direction of the lighter block. The velocity of the centre of mass is: (a) 30 m/s (b) 20 m/s (c) 10 m/s (d) 5 m/s PHYSICS Topic: CENTRE OF MASS, CONSERVATION OF MOMENTUM, COLLISION Date: 8. A machine gun fires a steady stream of bullets at the rate of n per minute into a stationary target in which the bullets get embedded. If each bullet has a mass m and arrives at the target with a velocity v, the average force on the target is : 60v mnv mv (a) 60 mnv (b) mn (c) 60 (d) 60n 9. A block of mass m moving at a velocity v collides with another block of mass 2m at rest. The lightest block comes to rest after collision. Find the coefficient of restitution : 1 1 1 (a) 2 (b) 1 (c) 3 (d) 4 10. Four particles of mass m1 = 2m, m2 = 4m, m3 = m and m4 are placed at four corners of a square. What should be the value of m4 so that the centre of mass of all the four particles are exactly at the centre of the square ? (a) 2 m (b) 8 m (c) 6 m (d) none of these PHYSICS Topic: CENTRE OF MASS, CONSERVATION OF MOMENTUM, COLLISION Date: Answer Key 1. (d) 2. (b) 3. (c) 4. (a) 5. (a) 6. (b) 7. (c) 8. (c) 9. (a) 10. (d)

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