JEE Physics System Of Particles and Rotational Motion MCQs Set B

Question. A particle undergoes uniform circular motion. About which point in the plane of the circle, will the angular momentum of the particle remain conserved?
(a) Centre of the circle
(b) Inside the circle other than centre
(c) On the circumference of the circle
(d) Outside the circle

Answer: A

Question. When a planet moves around sun, then its
(a) Areal velocity is constant
(b) Linear momentum is conserved
(c) Linear velocity is constant
(d) Angular velocity is constant

Answer: A

Question. When a rolling body enters onto a smooth horizontal surface, it will
(a) Continue rolling
(b) Come to rest
(c) Starts slipping
(d) Slipping as well as rolling

Answer: A

Question. A cylinder rolls down two different inclined planes of the same height but of different inclinations
(a) The time of descent will be different but speed will be same
(b) The speed will be different but time of descent will be same
(c) In both cases the speed and time of descent will be same
(d) In both cases the speed and time of descent will be different

Answer: A

Question. A disc of mass 3 kg rolls down an inclined plane of height 5 m. The translational kinetic energy of the disc on reaching the bottom of the inclined plane is
(a) 100 J
(b) 150 J
(c) 175 J
(d) 50 J

Answer: A

Question. Two persons of masses 55 kg and 65 kg respectively, are at the opposite ends of a boat. The length of the boat is 3.0 m and weighs 100 kg. The 55 kg man walks up to the 65 kg man and sits with him. If the boat is in still water the center of mass of the system shifts by
(a) Zero
(b) 0.75 m
(c) 3.0 m
(d) 2.3 m

Answer: A

Question. The centre of mass of a solid cone along the line from the center of the base to the vertex is at
(a) One-fourth of the height
(b) None of these
(c) One-fifth of the height
(d) One-third of the height

Answer: A

Question. The centre of mass of a system of particles does not depend on
(a) Forces acting on the particles
(b) Relative distances between the particles
(c) Position of the particles
(d) Masses of the particles

Answer: A

Question. Three masses are placed on the x-axis ; 300 g at origin, 500 g at x = 40 cm and 400 g at x = 70 cm. The distance of the centre of mass from the origin is
(a) 40 cm
(b) 45 cm
(c) 50 cm
(d) 30 cm

Answer: A

Question. Three identical metal balls, each of the radius r are placed touching each other on a horizontal surface such that an equilateral triangle is formed when centres of three balls are joined. The centre of the mass of the system is located at
(a) Point of intersection of the medians
(b) Centre of one of the balls
(c) Line joining centres of any two balls
(d) Horizontal surface

Answer: A

Question. A rod of length 3 m has its mass per unit length directly proportional to distance x from one of its ends then its centre of gravity from that end will be at
(a) 2 m
(b) 1.5 m
(c) 2.5 m
(d) 3.0 m

Answer: A

Question. Two particles which are initially at rest, move towards each other under the action of their internal attraction. If their speeds are v and 2v at any instant, then the speed of centre of mass of the system will be
(a) Zero
(b) 1.5 v
(c) 2 v
(d) v

Answer: A