The speed of earth s rotation about its axis is o. Its speed

Subject

Physics

Class

NEET Class 12

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 Multiple Choice QuestionsMultiple Choice Questions

1.

For inelastic collision between two spherical rigid bodies

  • the total kinetic energy is conserved

  • the total mechanical energy is not conserved

  • the linear momentum is not conserved

  • the linear momentum is conserved


2.

For a satellite moving in an orbit around the earth, the ratio of kinetic energy to potential energy is

  • 2

  • 12

  • 12

  • 2


3.

300 J of work is done in sliding a 2 kg block up an inclined plane of height 10 m. Taking g =10 m/s2, work done against friction is

  • 200J

  • 100 J

  • zero

  • 1000 J


4.

A particle moves along a straight line OX. At a time t (in second) the distance x ( in metre ) of the particle from O is given by x = 40 + 12 t - t3 . How long would the particle travel before coming to rest?

  • 24 m

  • 40 m

  • 56 m

  • 16 m


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5.

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


6.

The displacement of particle is given by x = αo+ α1t2 - α2t23 .What is its acceleration?

  • 2α23

  • -2α23

  • α2

  • Zero


7.

The area of the acceleration-displacement curve of a body gives

  • impulse

  • change in momentum per unit mass

  • change in KE per unit mass

  • total change in energy


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8.

The speed of earth's rotation about its axis is o. Its speed is increased to x times to make the effective acceleration due to gravity equal to zero at the equator. Then x is

  • 1

  • 8.5

  • 17

  • 34


C.

17

Earth rotates about its own axis in 24 h.

So,            T =24 x 60 x 60 s

So, angular speed of earth about its own axis

              ω = 2πTω = 2π24 × 60 × 60rad/s   

At equator  g' = g - Re ω'2

                0 = g - Reω'2 ω' = gRe          = 2π84.6 × 60  ω'ω = 24 ×60 × 6084.6 × 60

                          ≈ 17

                     ω' = 17ω

So, value of x is 17.


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9.

A projectile is thrown in the upward direction making an angle of 60° with the horizontal direction with a velocity of 147 ms-1 Then the time after which its inclination with the horizontal is 45°, is

  • 15 s

  • 10.98 s

  • 5.49 s

  • 2.745 s


10.

A motor cycle is going on an overbridge of radius R. The driver maintains a constant speed. As the motor cycle is ascending on the overbridge, the normal force on it

  • increases

  • decreases

  • remains the same

  • fluctuates erratically


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