Previous year papers of Physics exam questions - 3

A body of moment of inertia of 3 kgm2 rotating with an angular velocity of 2rad/s has the same kinetic energy as a mass of 12 kg moving with a velocity of
(a) 1 m/s (b) 2 m/s
(c) 4 m/s (d) 8 m/s
Answer: (a)

If a gymnast, sitting on a rotating stool, with his arms outstretched, suddenly lowers his arms (NCERT 78)
(a) The angular velocity decreases
(b) His moment of inertia decreases
(c) The angular velocity remains constant
(d) The angular momentum increases
Answer: (b)
The moment of inertia of a thin circular disc of mass M and radius R about any diameter is (MHT-CET-1999)
(a) (b)
(c) MR2 (d) 2MR2
Answer: (a)
A disc of radius R rotating about its axis has a moment of inertia I about that axis. When it is rotating about that axis at a constant angular velocity w a heavy particle of mass m is placed gently at the rim of the disc. The resulting angular velocity of the system is
(CPMT 91)
(a) w (b) Iw (I + mR)
(c) (I + mR)/Iw (d) Iw/(I + mR2)
Answer: (d)