Physics Objective type question bank -1

Radius of gyration of disc rotating about an axis perpendicular to its passing through its centre is
(a) (b) (c) (d)
Answer: (b)

The moment of inertia of a body about a given axis is 1.2 kg ´ metre2. Initially, the body is at rest. In order to produce a rotating kinetic energy of 1500 joules, an angular acceleration of 25 radian/sec2 must be applied about that axis for a duration of (CBSE 90)
(a) 4 sec (b) 2 sec
(c) 8 sec (d) 10 sec
Answer: (b)
M.I. of thin uniform rod about the axis passing through its centre and perpendicular to its length is The rod is cut transversely into two halves, which are then riveted end to end. M.I. of the composite rod about the axis passing through its centre and perpendicular to its length will be [MH-CET 2001]
(a) (b)
(c) (d)
Answer: (a)
A body having moment of inertia about its axis of rotation equal to 3 kg-m2 is rotating with angular velocity equal to 3 rad/s. kinetic energy of this rotating body is the same as that of a body of mass 27 kg moving with a speed of (SCRA 94)
(a) 1.0 m/s (b) 0.5 m/s
(c) 1.5 m/s (d) 2.0 m/s
Answer: (a)
For increasing the angular velocity of an object by 10%, the kinetic energy has to be increased by [MH-CET 2001]
(a) 40% (b) 20%
(c) 10% (d) 21%
Answer: (d)
When a torque acting upon a system is zero then the quantity which remains constant is (CPMT 79)
(a) Force (b) Linear impulse
(c) Linear momentum (d) Angular momentum
Answer: (a)
A tube of length L is filled completely with an incompressible liquid of mass M and closed at both the ends. The tune is then rotated in a horizontal plane about one of its end with a uniform angular velocityw. The force exerted by the liquid at the other end is, (IIT 92)
(a) (b) M w2 L
(c) (d)
Answer: (a)
Two discs has same mass rotates about the same axes. r1 and r2 are densities of two bodies (r1 > r2) then what is the relation between I1 and I2. (MHT-CET-2008)
(a) I1 > I2 (b) I1 < I2
(c) I1 = I2 (d) None of these
Answer: (b)
The momentum of inertia of a disc of mass M and radius R about a tangent in its plane is, (MP. PMT 96)
(a) (b)
(c) MR2 (d)
Answer: (d)
The M.I. of uniform circular disc about a diameter is I. its M.I. about an axis perpendicular to its plane passing through a point on its rim will be (CBSE 90, 91)
(a) 4 I (b) 6 I
(c) 8 I (d) 9 I
Answer: (b)