A black hole is an object whose gravitational field is so strong

Subject

Physics

Class

NEET Class 12

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 Multiple Choice QuestionsMultiple Choice Questions

1.

If force (F), velocity (v) and time (T) are taken as fundamental units, then the dimensions of mass are

  • [FvT-1]

  • [FvT-2]

  • [Fv-1T-1]

  • [Fv-1T-1]

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2.

A projectile is fired from the surface of the earth with a velocity of 5 m/s and angle straight theta with the horizontal. Another projectile fired from another planet with a velocity of 3 m/s at the same angle follows a trajectory which is identical with the trajectory of the projectile fired from the earth. The value of the acceleration due to gravity on the planet is,

  • 3.5

  • 5.9

  • 16.3

  • 16.3

1750 Views

3.

A particle is moving such that its position coordinates (x,y) are (2m, 3m) at time t = 0, (6m, 7m) at time t = 2 sec and (13 m, 14m) at time t= 5 sec. Average velocity vector (vav) from t = 0 to t = 5 s is,

  • 1 fifth left parenthesis 13 space i with hat on top space plus space 14 space j with hat on top right parenthesis
  • 7 over 3 open parentheses i with rightwards arrow on top space plus space j with hat on top close parentheses
  • 2 space left parenthesis straight i with hat on top space plus space straight j with hat on top right parenthesis
  • 2 space left parenthesis straight i with hat on top space plus space straight j with hat on top right parenthesis
1520 Views

4.

A system consists of three masses m1, m2 and m3 connected by a string passing over a pulley P. The mass m1 hangs freely and m2 and m3 are on a rough horizontal table (the coefficient of friction = μ). the pulley is frictionless and of negligible mass. The downward acceleration of mass m1 is,

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5.

The force F acting on a particle of mass m is indicated by the force-time graph as shown below. The climate change in momentum of the particle over the time interval from zero to 8 s is,

  • 24 Ns

  • 20 Ns

  • 12 Ns

  • 12 Ns

1949 Views

6.

A balloon with mass m is descending down with an acceleration a (where a <g). How much mass should be removed from it so that it starts moving up with an acceleration a?

900 Views

7.

A body of mass (4m) is lying in x-y plane at rest. It suddenly explodes into three pieces. Two pieces each of mass m move perpendicular to each other with equal speed (v). The total kinetic energy generated due to explosion is,

  • mv2

  • 3 over 2 m v squared
  • 2mv2

  • 2mv2

1061 Views

8.

A solid cylinder of mass 50 kg and radius 0.5 m is free to rotate about the horizontal axis. A massless string is wound around the cylinder with one end attached to it and other hanging freely. Tension in the string required to produce an angular acceleration of 2 rev/s2 is,

  • 25 N

  • 50 N

  • 78.5 N

  • 78.5 N

2801 Views

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9.

The ratio of the accelerations for a solid sphere (mass m and radius R) rolling down an incline of angle straight theta without slipping and slipping down the incline without rolling is,

  • 5:7

  • 2:3

  • 2:5

  • 2:5

2280 Views

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10.

A black hole is an object whose gravitational field is so strong that even light cannot escape from it. To what approximate radius would earth (mass = 5.98 x 1024 kg) have to be compressed to be a black hole?

  • 10-9 m

  • 10-6 m

  • 10-2 m

  • 10-2 m


C.

10-2 m

For a black hole, escape speed is more than the speed of light.

Escape velocity is given by,


Approximating the escape velocity to the speed of light, we have

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