Two small spheres of masses M1 and M2 are suspended by weigh

Subject

Physics

Class

JEE Class 12

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 Multiple Choice QuestionsMultiple Choice Questions

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1.

Two small spheres of masses M1 and M2 are suspended by weightless insulating threads of lengths L1 and L2. The spheres carry charges Q1 and Q2 respectively. The spheres are suspended such that they are in level with one another and the threads are inclined to the vertical at angles of θ1 and θ2 as shown. Which one of the following conditions is essential, if θ1 = θ2 ?

               

  • M1 ≠ M2, but Q1 = Q2

  • M1 = M2

  • Q1 = Q2

  • L1 = L2


B.

M1 = M2

For sphere 1, in equilibrium

     

     T1 cos θ1 = M1g

and T1 sin θ= F1

             tan θ1 = F1M1g

Similarly, for sphere 2, tan θ2 = F2M2g

F is same on both the charges, θ will be same only if their masses M are equal.


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2.

The moment of inertia of a circular disc of radius 2 m and mass 1 kg about an axis passing through the centre of mass but perpendicular to the plane of the disc is 2 kg m2. Its moment of inertia about an axis parallel to this axis but passing through the edge of the disc is (see the given figure).

           

  • 8 kg m2

  • 4 kg m2

  • 10 kg m2

  • 6 kg m2


3.

An astronaut on a strange planet finds that acceleration due to gravity is twice as that on the surface of earth. Which of the following could explain this ?

  • Both the mass and radius of the planet are half as that of earth

  • Radius of the planet is half as that of earth, but the mass is the same as that of earth

  • Both the mass and radius of the planet are twice as that of earth

  • Mass of the planet is half as that of earth, but radius is same as that of earth


4.

The dimensions of resistance are same as those of where h is the Planck's constant, e is the charge.

  • h2e2

  • h2e

  • he2

  • he


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5.

A train is moving slowly on a straight track with a constant speed of 2 ms-1. A passenger in that train starts walking at a steady speed of 2 ms-1 to the back of the train in the opposite direction of the motion of the train. So to an observer standing on the platform directly in front of that passenger, the velocity of the passenger appears to be

  • 4 ms-1

  • 2 ms-1

  • 2 ms-1 in the opposite direction of the train

  • zero


6.

A ball rests upon a flat piece of paper on a table top. The paper is pulled horizontally but quickly towards right as shown relative to its initial position with respect to the table, the ball

               

  1. remains stationary if there is no friction between the paper and the ball
  2. moves to the left and starts rolling backwards, i.e, to the left if there is a friction between the paper and the ball.
  3. moves forward, i.e, in the direction in which the paper is pulled.

Hence, the correct statement is/are

  • Both (1) and (2)

  • only (3)

  • only (1)

  • only (2)


7.

A boy throws a cricket ball from the boundary to the wicket-keeper. If the frictional force due to air cannot be ignored, the forces acting on the ball at the position X are respected by

              


8.

If the linear momentum of a body is increased by 50%, then the kinetic energy of that body increases by

  • 100 %

  • 125 %

  • 225 %

  • 25 %


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9.

A motorboat covers a given distance in 6 h moving downstream on a river. It covers the same distance in 10 h moving upstream. The time it takes to cover the same distance in still water is

  • 9 h

  • 7.5 h

  • 6.5 h

  • 8 h


10.

Two simple harmonic motions are represented by

       y1 = 5 sin 2πt + 3 cos 2πtand y2 = 5 sin 2πt + π4

The ratio of their amplitudes is

  • 1 : 1 

  • 2 : 1

  • 1 : 3

  • 3 : 1


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