A coin placed on a rotating turntable just slips if it is placed

Subject

Physics

Class

NEET Class 12

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 Multiple Choice QuestionsMultiple Choice Questions

1.

A body of mass m is moving towards the east and another body of equal mass is moving towards the north. If after collision both stick together, their speed after collision would be :

  • v

  • v/2

  • 2v

  • v2


2.

A body of mass 1 kg is moving in a vertical circular path of radius 1 m. The difference between the kinetic energies at its highest and lowest position is :

  • 20 J

  • 10 J

  • 45 J

  • 10(5 - 1) J


3.

Two bodies are thrown up at angles of 40° and 60°, respectively, with the horizontal. If both bodies attain the same vertical height, then the ratio of velocities with which these are thrown is:

  • 23

  • 23

  • 32

  • 32


4.

Escape velocity from a planet is v, If its mass is increased to 8 times and its radius is increased to 2 times, then the new escape velocity would be :

  • ve

  • 2ve

  • 2ve

  • 22ve


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5.

A body takes time t to reach the bottom of an inclined plane of angle 0 with the horizontal. If the plane is made rough, time taken now is 2t. The coefficient of friction of the rough surface is:

  • 34tanθ

  • 23tanθ

  • 14tanθ

  • 12tanθ


6.

Acceleration due to gravity:

  • decreases from the equator to poles

  • decreases from poles to the equator

  • is maximum at the centre of the earth

  • is maximum at the equator


7.

Two bodies having masses m1 = 40g and m2 = 60 g are attached to the ends of a string of negligible mass and suspended from a massless pulley. The acceleration of the bodies is:

  • 1 m/s2

  • 2 m/s2

  • 0.4 m/s2

  • 4 m/s2


8.

A block is moving up an inclined plane of inclination 60° with a velocity of 20 m/s and stops after 2 s. If g = 20 m/s2 then the approximate value of the coefficient of friction is :

  • 3

  • 3.3

  • 0.27

  • 0.33


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9.

A coin placed on a rotating turntable just slips if it is placed at a distance of 8 cm from the centre. If angular velocity of the turntable is doubled, it will just slip at a distance of :

  • 1 cm

  • 2 cm

  • 4 cm

  • 8 cm


B.

2 cm

We know F = mrω2

2 = constant

ω2 ∝ 1/r

 ω2ω12 = r1r24ω12ω12 = 8r2 r2 = 2 cm


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10.

When a man increases his speed by 2 m/s, he finds that his kinetic energy is doubled, the original speed of the man is :

  • 2(2 - 1) m/s

  • 2(2 + 1) m/s

  • 4.5 m/s

  • none of these


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