Physics-DPP-2-Rotational Motion

PHYSICS Topic: ROTATIONAL MOTION Date: 1. A 70 kg man standing on ice throws a 3 kg body horizontally at 8 m/s. The friction coefficient between the ice and his feet is 0.02. The distance, the man slips is : (a) 0.3 m (b) 2 m (c) 1 m (d) ¥ 2. Mass of bigger disc having radius 2 R is M. A disc of radius R is cut from bigger disc as shown in figure. Moment of inertia of disc about an axis passing through periphery and perpendicular to plane (shown in figure) is : (a) 27 MR 2 8 (b) 29 MR 2 8 (c) 3.5 MR2 (d) 2 MR2 3. The ratio of the radii of gyration of a circular disc and a circular ring of the same radii about a tangential axis in the plane is : (a) 1 : 2 (b) 5 : 6 (c) 2 : 3 (d) 2 : 1 4. Two uniform rods of equal length but different masses are rigidly joined to form an L-shaped body, which is then pivoted as shown. If in equilibrium the body is in the shown configuration, ratio M/m will be : (a) 2 (b) 3 (c) 2 (d) 3 5. Two halves of a round homogeneous cylinder are held together by a thread wrapped round the cylinder with two equal weights. The complete cylinder weighs 31.4 kg. The plane of contact of both of its halves is vertical. For equilibrium of both halves of the cylinder, the minimum value of m is : (a) 2 g (b) 3.14 g (c) 2 kg (d) 31.4 g 3 3 PHYSICS Topic: ROTATIONAL MOTION Date: 6. A rectangular plate of mass 20 kg is suspended from points A and B as shown. If the point B is suddenly removed, determined the angular acceleration (in rad/s2) of the plate : (a) 48 (b) 19.6 (c) 29.4 (d) 23.6 7. A uniform rod of length l and mass m is suspended by two vertical inextensible strings as shown in figure. Then tension in the left string when right string snaps is : (a) 3mg 4 mg (b) 4 mg (c) 2 mg (d) 8 8. A solid sphere of radius R is resting on a smooth horizontal surface. A constant force F is applied at a height h from the bottom. Choose the correct alternative. (a) Sphere will always slide whatever be the value of h (b) Sphere will roll without slipping when h ³ 1.4 R (c) Sphere will roll without slipping if h = 1.4 R (d) None of the above 9. A weightless rod of length l carries two equal masses m one fixed at the end and other in the middle of the rod. The rod can revolve in a vertical plane about A. Then horizontal velocity which must be imparted to end C of rod to deflect it to horizontal position is : (i) (b) (c) (d) PHYSICS Topic: ROTATIONAL MOTION Date: 10. A simple pendulum is vibrating with an angular amplitude of 90o as shown in the figure. For what value of α , the acceleration is directed horizontally ? (a) 0 (b) 90o (c) cos–1 æç 1 ö÷ (d) sin –1 æç 1 ö÷ PHYSICS Topic: ROTATIONAL MOTION Date: Answer Key 1. (a) 2. (b) 3. (b) 4. (d) 5. (c) 6. (a) 7. (b) 8. (c) 9. (a) 10. (c)