JEE Questions for Physics Systems Of Particles And Rotational Motion Quiz 5 - MCQExams.com

A 10 kg body hangs at rest from a rope wrapped around a cylinder 0.2 m in diameter. The torque applied about the horizontal axis of the cylinder is
  • 98 N-m
  • 19.6 N-m
  • 196 N-m
  • 9.8 N-m
Which is a vector quantity ?
  • Work
  • Power
  • Torque
  • Gravitational constant
When a torque acting upon a system is zero, then which of the following will be constant ?
  • Force
  • Linear momentum
  • Angular momentum
  • Linear impulse
The instantaneous angular position is a point on a rotating wheel is given by the equation θ(t) = 2t3 – 6t2. The torque on the wheel becomes zero at
  • t = 2s
  • t = 1s
  • t = 0.2s
  • t = 0.25s
A disc is rotating with an angular speed of ω. If a child sits on it, which of the following is conserved ?
  • Linear momentum
  • Kinetic energy
  • Potential energy
  • Angular momentum
If the radius of the earth is suddenly contracts to half of its present value, then the duration of day will be of
  • 6 hr
  • 12 hr
  • 18 hr
  • 24 hr
The moment of momentum is called
  • Couple energy
  • Torque
  • Impulse
  • Angular momentum
Two bodies have their moment of inertia I and 2I respectively about their axis of rotation. If their kinetic energies of rotation are equal, their angular momentum will be in the ratio
  • 1 : 2
  • √2 : 1
  • 2 : 1
  • 1 : √2
The radius of a rotating disc is suddenly reduced to half without any change in its mass. Then its angular velocity will be
  • Four times
  • Double
  • Half
  • Unchanged
Before jumping in water from above a swimmer bends his body to
  • Increase moment of inertia
  • Decrease moment of inertia
  • Decrease the angular momentum
  • Reduce the angular velocity
If the angular momentum of any rotating body increases by 200%, then the increase in its kinetic energy
  • 400 %
  • 800 %
  • 200 %
  • 100 %
In an orbital motion, the angular momentum vector is
  • Along the radius vector
  • Parallel to the linear momentum
  • In the orbital plane
  • Perpendicular to the orbital plane
Angular momentum L of body with mass moment of inertia I and angular velocity ω rad/sec is equal to
  • I/ω
  • Iω2
  • Iω
  • None of these
A solid sphere of mass 500 g and radius 10 cm rolls without slipping with the velocity 20 cm/s. The total kinetic energy of the sphere will be
  • 0.014 J
  • 0.028 J
  • 280 J
  • 140 J
Ratio of total kinetic energy and rotational kinetic energy in the motion of a disc is
  • 1 : 1
  • 2 : 7
  • 1 : 2
  • 3 : 1
A body of moment of inertia of 3 kg-m2 rotating with an angular velocity of 2 rad/sec has the same kinetic energy as a mass of 12 kg moving with a velocity of
  • 8 m/s
  • 0.5 m/s
  • 2 m/s
  • 1 m/s
The moment of inertia of a flywheel having kinetic energy 360 J and angular speed of 20 rad/s is
  • 18 kg m2
  • 1.8 kg m2
  • 2.5 kg m2
  • 9 kg m2
If rotational kinetic energy is 50% of translational kinetic energy, then the body is
  • Ring
  • Cylinder
  • Hollow sphere
  • Solid sphere
In the above question, find the angular speed at the bottom
  • 68 rad/sec
  • 8.5 rad/sec
  • 17 rad/sec
  • 34 rad/sec
A mass m is moving with a constant velocity along a line parallel to x-axis. Its angular momentum with respect to origin or z-axis is
  • Zero
  • Remains constant
  • Goes on increasing
  • Goes on decreasing
A small disc of radius 2 cm is cut from a disc of radius 6 cm. If the distance between their centres is 3.2 cm, what is the shift in the centre of mass of the disc?
  • 0.4 cm
  • 2.4 cm
  • 1.8 cm
  • 1.2 cm
A wheel of moment of inertia 5 × 10–3 kg–m2 is making 20 revolutions per second.It is stopped in 20 sec, then the angular retardation is
  • π rad/sec2
  • 2π rad/sec2
  • 4π rad/sec2
  • 8π rad/sec2
The flywheel is so constructed that the entire mass of it is concentrated at its rim, because
  • It increases the power
  • It increases the speed
  • It increases the moment of inertia
  • It saves the flywheel fan from breakage
A reel of thread unrolls itself falling down under gravity. Neglecting mass of the thread, the acceleration of the reel is
  • g
  • g/2
  • 2g/3
  • 4g/3
When a uniform solid sphere and a disc of the same mass and of the same radius rolls down an inclined smooth plane from rest to the same distance, then the ratio of the time taken by them is
  • 15 : 14
  • 152 : 142

  • Physics-Systems of Particles and Rotational Motion-89113.png
  • 14 : 15
Two discs have same mass and thickness. Their materials are of densities ρ1 and ρ2. The ratio of their moment of inertia about central axis will be
  • ρ1 : ρ2
  • ρ1 ρ2 : 1
  • 1 : ρ1 ρ2
  • ρ2 : ρ1
The centre of mass of a body
  • Lies always outside the body
  • May lie within, outside on the surface of the body
  • Lies always inside the body
  • Lies always on the surface of the body
Two spheres of masses 2M and M are initially at rest at a distance R apart. Due to mutual force of attraction, they approach each other. When they are at separation R/2, the acceleration of the centre of mass of spheres would be
  • 0 m/s2
  • g m/s2
  • 3g m/s2
  • 12 g m/s2
An isolated particle of mass m is moving in a horizontal plane (X – Y) along the X-axis at a certain height above the ground. It suddenly explodes into two fragments of masses m/4 and 3m/4. An instant later, the smaller fragment is at y = 15 cm. The larger fragment of this instant is at
  • y = – 5 cm
  • y = +20 cm
  • y = +5 cm
  • y = – 20 cm
Four point masses P, Q, R and S with respective masses 1 kg, 1 kg, 2 kg and 2 kg from the corners of a square of side a. The centre of mass of the system will be farthest from
  • P only
  • R and S
  • R only
  • P and Q
A particle moves along a circle of radius 20/π m with constant tangential acceleration. If the velocity of the particle is 80 m/s at the end of the second revolution after motion has begin, the tangential acceleration is
  • 640 π m/s2
  • 160 π m/s2
  • 40 π m/s2
  • 40 m/s2
In rotational motion of a rigid body, all particles move with
  • Same linear and angular velocity
  • Same linear and different angular velocity
  • With different linear velocities and same angular velocities
  • With different linear velocities and different angular velocities
A constant torque of 1000N-m turns a wheel of moment of inertia 200 kg-m2 about an axis through its centre. Its angular velocity after 3 sec is
  • 1 rad/sec
  • 5 rad/sec
  • 10 rad/sec
  • 15 rad/sec
A car is moving at a speed of 72 km/hr. The radius of its wheels is 0.25 m. If the wheels are stopped in 20 rotations by applying brakes, then angular retardation produced by the brakes is
  • –25.5 rad/s2
  • –29.5 rad/s2
  • –33.5 rad/s2
  • –45.5 rad/s2
A wheel is rotating at 900 r.p.m. about its axis. When the power is cut-off, it comes to rest in 1 minute. The angular retardation in radian/s2 is
  • π / 2
  • π / 4
  • π / 6
  • π / 8
In which case application of angular velocity is useful
  • When a body is rotating
  • When velocity of body is in a straight line
  • When acceleration of body is in a straight line
  • None of the above
A wheel rotates with a constant acceleration of 2.0 radian/sec2. If the wheel starts from rest the number of revolutions it makes in the first ten seconds will be approximately
  • 8
  • 16
  • 24
  • 32
The angular momentum of a wheel changes from 2L to 5L in 3 seconds. What is the magnitude of the torque acting on it?
  • L
  • L/2
  • L/3
  • L/5
A mass is revolving in a circle which is in the plane of paper. The direction of angular acceleration is
  • Upward the radius
  • Towards the radius
  • Tangential
  • At right angle to angular velocity
The direction of the angular velocity vector is along
  • The tangent to the circular path
  • The inward radius
  • The outward radius
  • The axis of rotation
A round uniform body of radius R, mass M and moment of inertia I, rolls down (without slipping) an inclined plane making an angle θ with the horizontal. Then its acceleration is

  • Physics-Systems of Particles and Rotational Motion-89124.png
  • 2)
    Physics-Systems of Particles and Rotational Motion-89125.png

  • Physics-Systems of Particles and Rotational Motion-89126.png

  • Physics-Systems of Particles and Rotational Motion-89127.png
Two identical discs of same radius R are rotating about their axes in opposite directions with the same constant angular speed ω. The discs are in the same horizontal plane. At time t = 0, the points P and Q are facing each other as shown in the figure.The relative speed between the two points P and Q is vr . In one time period (T) of rotation of the discs, vr as a function of time is best represented by
Physics-Systems of Particles and Rotational Motion-89129.png

  • Physics-Systems of Particles and Rotational Motion-89130.png
  • 2)
    Physics-Systems of Particles and Rotational Motion-89131.png

  • Physics-Systems of Particles and Rotational Motion-89132.png

  • Physics-Systems of Particles and Rotational Motion-89133.png
A car of mass 2000 kg is moving with a speed of 10 ms-1 on a circular path of radius 20m on a level road. What must be the frictional force between the car and the road so that the car does not slip ?
  • 104 N
  • 103 N
  • 105 N
  • 102 N
A car of mass 1000 kg moves on a circular track of radius 20 m. If the coefficient of friction is 0.64, then the max. velocity with which the car can move is
  • 22.4 m/s
  • 5.6 m/s
  • 11.2 m/s
  • none of the above
A solid cylinder of mass 20 kg rotates about its axis with angular speed 100 rad/s. The radius of the cylinder is 0.25 m. The K.E. associated with the rotation of the cylinder is
  • 3025 J
  • 3225 J
  • 3250 J
  • 3125 J
A bucket tied at the end of a 1.6 m long string is whirled in a vertical circle with a constant speed. The minimum speed at which water from the bucket does not spil when it is at the highest position is
  • 4 m/s
  • 6.25 m/s
  • 2 m/s
  • 16 m/s
A frictionless track ABCDE ends in a circular loop of radius R. A body slides down the track from A, which is at a height h = 5 cm. Maximum value of R for a body to complete the loop successfully is
Physics-Systems of Particles and Rotational Motion-89139.png
  • 2 cm
  • 10/3 cm
  • 15/4 cm
  • 6 cm
A nut bolt system has 20 threads per cm. Find the time taken to travel the nut 4 cm if it moves in the bolt at a rate 4 rots/sec.
  • 80 s
  • 40 s
  • 30 s
  • 20 s

Physics-Systems of Particles and Rotational Motion-89142.png

  • Physics-Systems of Particles and Rotational Motion-89143.png
  • 2)
    Physics-Systems of Particles and Rotational Motion-89144.png

  • Physics-Systems of Particles and Rotational Motion-89145.png
  • none of these
Two particles A and B initially at rest move towards each other under a mutual force of attraction. At the instant when velocity of A is υ and that of B is 2 υ, the velocity of centre of mass of the system is
  • v
  • 2v
  • 3v
  • zero
0:0:1


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