Newton's Second Law: Rotatory Version
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Q.
An object is attached to a vertical spring and slowly lowered to its equilibrium position. This stretches the spring by an amount d. If the same object is attached to the same vertical spring but permitted to fall instead. Through what distance does it stretch the spring?
d
2d
3
5d
Q. A uniform disc of mass M and radius R is free to rotate about its fixed horizontal axis without friction. There is sufficient friction between the inextensible light string and the disc to prevent slipping of the string over the disc. At the shown instant, extension in the light spring is 3mgK, where m is the mass of the block, g is acceleration due to gravity and K is spring constant. Then, the acceleration of block just after it is released is
- 2g3
- 4g3
- 5g3
- g3
Q. VIOIONTarlane12. Three forces given by vectors 2i+2j, 2i-2j and - 4i are acting together on a point object at rest. The objectmoves along the direction(1) x-axis(2) y-axis(3) z-axis(4) Object does not move
Q. 90.A particle moves in X-Y plane under action of force F such that linear momentum P at any time t is 2costi +2sintj the angle between F and P at given time t is
Q. work done by kinetic friction?
Q. Angular momentum of body about a point A is given as →L=(4t2+6)^k. Find the net torque acting on body about point A at t=3 sec.
- 8^k Nm
- 4^k Nm
- 24^k Nm
- 20^k Nm
Q. A cotton reel of mass m and moment of inertia 2 kgm2 is kept at rest on a smooth horizontal surface. The reel has inner radius 0.2 m and outer radius 0.5 m. A horizontal force F=200 N starts acting as shown is the figure. Find the angular acceleration of the reel.
- 50 rad/s2
- 20 rad/s2
- 40 rad/s2
- 100 rad/s2
Q. Magnitude of acceleration of the two blocks is :
(Radius of pulley is 1 m)
(Radius of pulley is 1 m)
- 3 m/s2
- 1.5 m/s2
- 2 m/s2
- 2.5 m/s2
Q.
A constant force 'F' is applied at the top of a ring as shown in figure. Mass of the ring is 'M' and radius is 'R'. Angular momentum of particle about point of contact at time 't' is
- Is constant
- Increases linearly with time
- Is Zero
- Decreases linearly with time
Q. 25.Two rotating bodies A and B of masses m and 2m with moments of inertia IA and IB (IB > IA) have equal kinetic energy of rotation . If LA and LB be their angular momenta respectively then 1- LA = LB/2 2- LA= 2LB 3- LB > LA 4- LA > LB
Q. 2A body is initially at rest. It undergoes onedimensional motion with constant acceleration. Thepower delivered to it at time t is proportional to1(1) t2(2) t3(3) t2(4)
Q.
PHYSICS
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Asked on December 27, 2019 by
Nikunj Vjaya
A rigid body of mass 0.3 kg is taken slowly up an inclined plane of length 10 m and height 5 m (assuming the applied force to be parallel to the inclined plane), and then allowed to slide down to the bottom again. The coefficient of friction between the body and the plane is 0.15. using g = 9.8 m/s
2
find the
(a) work done y the gravitational force over the round trip
(b) work done by the applied force over the upward journey
(c) work done by frictional force over the round trip
(d) kinetic energy of the body at the end of the trip?
Q. A bullet of mass 20 g travelling horizontally with a speed of 500 m/s passes through a wooden block of mass 10.0 kg initially at rest on a level surface. The bullet emerges with a speed of 100 m/s and the block slides 20 cm on the surface before coming to rest. Find the friction coefficient between the block and the surface.
Figure
Figure
Q. 116.Two blocks A and B each of mass 1 kg placed on a smooth horizontal surface. Two horizontal forces 5 N and 10 N are applied on the blocks A and B respectively as shown in figure. The block A does not slide on block B. Then the normal reaction acting between the two block is
Q. 121. A toy car with charge q moves on a frictionless horizontal plane surface under the influence of a uniform electric field E. Due to the force qE, its velocity increase from 0 to 6 M/s in one second duration. At that instant the direction of the field is reversed. The car continues to move for two more second under the influence of this field . The average velocity and the average speed of the toy car between 0 to 3 second are respectively.
Q. A thin uniform rod, pivoted at O, is rotating in the horizontal plane with constant angular speed ω, as shown int he figure. At time t = 0, a small insect starts from O and moves with constant speed v with respect to the rod towards the other end. It reaches the end of the rod at t = T and stops. The angular speed of the system remains ω throughout. The magnitude of the torque (→τ) on the system about O, as a function of time is best represented by which plot?
Q.
Which of following rotational physical quantities do not match to given translational analogies?
Angular velocity-linear velocity
Angular displacement - linear displacement
Torque - Kinetic Energy
Moment of Inertia - mass
Q. A wheel having moment of inertia (I=2 kg-m2) is rotating about its natural axis. The instantaneous angular velocity of a point on a rotating wheel is given by the equation ω(t)=(2t2+4) rad/s. Find the torque acting on wheel about its axis of rotation at t=2 s.
- 14 Nm
- 12 Nm
- 10 Nm
- 16 Nm
Q. A boy of mass M is applying a horizontal force to slide a box of mass M on a rough horizontal surface. The coefficient of friction between the shoes of the boy and the floor is μ and that between the box and the floor is μ. In which of the following cases it is certainly not possible to slide the box?
(a) μ < μ, M < M
(b) μ > μ, M < M
(c) μ < μ, M > M
(d) μ > μ, M > M
(a) μ < μ, M < M
(b) μ > μ, M < M
(c) μ < μ, M > M
(d) μ > μ, M > M