JEE Physics System Of Particles and Rotational Motion MCQs Set A

Question. Two particles A and B initially at rest move towards each other under a mutual force of attraction. At the instant when velocity of A is v and that of B is 2v, the velocity of centre of mass of the system
(a) Zero
(b) 3v
(c) 2v
(d) v

Answer: A

Question. A shell following a parabolic path explodes somewhere in its flight. The centre of mass of fragments will move in
(a) Same parabolic path
(b) Horizontal direction
(c) Any direction
(d) Vertical direction

Answer: A

Question. The moment of inertia of a body depends on
(a) All of these
(b) The distribution of the mass in the body
(c) The mass of the body
(d) The axis of rotation of the body

Answer: A

Question. A circular disc is to be made by using iron and aluminium so that it possesses maximum moment of inertia about geometrical axis. It is possible with
(a) Aluminium at interior and iron surrounding it
(b) Iron at interior surrounded by aluminium
(c) Using iron and aluminium layers in alternate order
(d) Sheet of iron is used at both external surfaces and aluminium as interior layer

Answer: A

Question. An angular impulse of 20 Nms is applied to a hollow cylinder of mass 2 kg and radius 20 cm. The change in its angular speed is
(a) 250 rad/s
(b) 2500 rad/s
(c) 2.5 rad/s
(d) 25 rad/s

Answer: A

Question. A hollow sphere of mass 1 kg and radius 10 cm is free to rotate about its diameter. If a force of 30N is applied tangentially to it, its angular acceleration is (in rad/s²)
(a) 450
(b) 50
(c) 5
(d) 5000

Answer: C

Question. Two like parallel forces 20 N and 30 N act at the ends A and B of a rod 1.5 m long. The resultant of the forces will act at the point
(a) 90 cm from A
(b) 75 cm from B
(c) 20 cm from B
(d) 85 cm from A

Answer: A

Question. A solid sphere, a spherical shell, a ring and a disc of same radius and mass are allowed to roll down an inclined plane without slipping. The one which reaches the bottom first is
(a) Solid sphere
(b) Spherical shell
(c) Ring
(d) Disc

Answer: A

Question. If torque acting upon a system is zero, the quantity that remains constant is
(a) Angular momentum
(b) Angular velocity
(c) Linear momentum
(d) Force

Answer: A

Question. A meter stick is held vertically with one end on the floor and is allowed to fall. The speed of the other end when it hits the floor assuming that the end at the floor does not slip is (g = 9.8 m/s²)
(a) 5.4 m/s
(b) 7.6 m/s
(c) 9.2 m/s
(d) 3.2 m/s

Answer: A

Question. A metre stick is pivoted about its centre. A piece of wax of mass 20 g travelling horizontally and perpendicular to it at 5 m/s strikes and adheres to one end of the stick so that the stick starts to rotate in a horizontal circle. Given the moment of inertia of the stick and wax about the pivot is 0.02 kg m2, the initial angular velocity of the stick is
(a) 2.50 rad/s
(b) 5.00 rad/s
(c) 2.24 rad/s
(d) 1.58 rad/s

Answer: A

Question. A circular disc of mass 2 kg and radius 10 cm rolls without slipping with a speed 2 m/s. The total kinetic energy of disc is
(a) 6 J
(b) 2 J
(c) 4 J
(d) 10 J

Answer: A

Question. When a body is rolling without slipping on a rough horizontal surface, the work done by friction is
(a) Always zero
(b) May be zero
(c) Always positive
(d) Always negative

Answer: A

Question. A swimmer while jumping into river from a height easily forms a loop in air if
(a) He pulls his arms and legs in
(b) He keeps himself straight
(c) He spreads his arms and legs
(d) None of these

Answer: A

Question. A man of mass 60 kg is standing on a boat of mass 140 kg, which is at rest in still water. The man is initially at 20 m from the shore. He starts walking on the boat for 4 s with constant speed 1.5 m/s towards the shore. The final distance of the man from the shore is
(a) 15.8 m
(b) 4.2 m
(c) 12.6 m
(d) 14.1 m

Answer: A

Question. Two blocks of masses 5 kg and 2 kg are connected by a spring of negilible mass and placed on a frictionless horizontal surface. An impulse gives a velocity of 7 m/s to the heavier block in the direction of the lighter block. The velocity of the centre of mass is
(a) 5 m/s
(b) 10 m/s
(c) 20 m/s
(d) 30 m/s

Answer: A

Question. Moment of inertia of a uniform circular disc about its diameter is I. Its moment of inertia about an axis parallel to its plane and passing through a point on its rim will be
(a) 6I
(b) 5I
(c) 4I
(d) 3I

Answer: A