A pulley of radius 2 m is rotated about its axis by a force F =20t-5t2 newton (where t is measured in seconds) applied tangentially. If the moment of inertia of the pulley about its axis of rotation is 10 kgm2, the number of rotations made by the pulley before its direction of motion it reversed, is
(a) more than 6 but less than 9
(b) more than 9
(c) less than 3
(d) more than 3 but less than 6
From a uniform circular disc of radius R and mass 9M, a small disc of radius R/3 is removed as shown in the figure. The moment of inertia of the remaining disc about an axis perpendicular to the plane of the disc and passing through the centre of the disc is
(a) (40/9)MR2
(b) 10MR2
(c) (37/9)MR2
(d) 4MR2
A bob of mass m attached to an inextensible string of length is suspended from a vertical support. The bob rotates in a horizontal circle with an angular speed ω rad/s about the vertical. About the point of suspension
(a) Angular momentum changes in direction but not in magnitude
(b) Angular momentum changes both in direction and magnitude
(c) Angular momentum is conserved
(d) Angular momentum changes in magnitude but not in direction.
ball of mass (m) 0.5 kg is attached to the end of a string having a length (L) 0.5 m. The ball is rotated on a horizontal circular path about a vertical axis. The maximum tension that the string can bear is 324 N. The maximum possible value of the angular velocity of ball (in radian/s) is
(a) 9
(b).18
(c) 27
(d) 36
A child is standing with folded hands at the centre of a platform rotating about its central axis. The kinetic energy of the system is K. The child now stretches his arms so that the moment of inertia of the system doubles. The kinetic energy of the system now is
A block of mass m is placed on a surface with a vertical cross-section given by y =x3/ 6. If the coefficient of friction is 0.5, the maximum height above the ground at which the block can be placed without slipping is
(a) ⅓ m
(b) ½ m
(c) ⅙ m
(d) ⅔ m
A body of mass m=10−2 kg is moving in a medium and experiences a frictional force F=−kv2. Its initial speed is v0= 10 ms−1. If, after 10 s, its energy is ⅛ mv02, the value of k will be
(a) 10−3 kg m−1
(b) 10−3 kg s−1
(c) 10−4 kg m−1
(d) 10−1 kg m−1 s−1
The minimum force required to start pushing a body up a rough (frictional coefficient μ) inclined plane F1 while the minimum force needed to prevent it from sliding down is F2. If the inclined plane makes an angle θ from the horizontal such that tan θ= 2μ then the ratio F1/F2 is
(a) 4
(b) 1
(c) 2
(d) 3
The upper half of an inclined plane with inclination Φ is perfectly smooth, while the lower half is rough. A body starting from rest at the top will again come to rest at the bottom, if the coefficient of friction for the lower half is given by
(a) 2 sinΦ
(b) 2 cosΦ
(c) 2 tanΦ
(d) tanΦ
A block rests on a rough inclined plane making an angle of 300 with the horizontal. The coefficient of static friction between the block and the plane is 0.8. If the frictional force on the block is 10 N, the mass of the block (in kg) is : (taken g =10 m/s2)
(a) 2.0
(b) 4.0
(c) 1.6
(d) 2.5
+91 94284 01196
© Copyright 2025. Doubtora. All Rights Reserved
