A particle moves towards east for 2 s with velocity 15 m/s a

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 Multiple Choice QuestionsMultiple Choice Questions

131.

A force F is given F = at + bt2 where, t is time. What are the dimensions of a and b?

  • [ M L T-1 ] and [M L To ]

  • [ M L T-3 ] and [ M L2 T-4 ]

  • [ M L T-4 ] and [ M L T1 ]

  • [ M L T-3 ] and [ M L T-4 ]


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132.

A particle moves towards east for 2 s with velocity 15 m/s and move towards north for 8 s with velocity 5 m/s. Then, average velocity of the particle is

  • 1 m/s

  • 5 m/s

  • 7 m/s

  • 10 m/s


B.

5 m/s

Distance covered towards east 

          = speed × time

          =  2 × 15 = 30 m

Distance covered towards north

         = speed × time

         = 8  × 5 = 40 m

Total displacement

          = 402 + 302

           = 50 m

Average velocity = Total displacementTotal time

                          = 502 + 8

                          = 5 m/s     


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133.

The distance x (in µm) covered by a molecule starting from point A at time t = 0 and stopping at another point B in given by the equation  x = t2 2 - t3 The distance between A and B ( in μm) is closed to

  • 10.7

  • 20.7

  • 40.7

  • 50.7


134.

The density of a rod having length l varies as ρ = c + dx, where x is the distance from the left end. The centre of mass is     

  • 3 cl + 2 D l23  2c + D l 

  • 2 cl + 3D I22  4c + 8I 

  • 2 cl + 3 DI23 2c + I

  • cl + DI22  2 c + DI 


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135.

A block is kept on the floor of an elevator at rest. The elevator starts descending with an acceleration of 12 m/s2. Find the displacement of the block during the first 0.2 s after the start. (Take, g = 10 m/s2)

  • 30 cm

  • zero

  • 20 cm

  • 25 cm


136.

A rod PQ of length l is moving with ends remaining in contact with frictionless wall and floor. If at the instant, shown the velocity of end Q is 2 m/s towards negative direction of x. The speed of end P will be

   

  • 3 ms-1

  • 23 ms-1

  • 2 ms-1

  • 52 ms-1


137.

The displacement x of a particle varies with time t as x = ae-αt + beβt where a, b, α and β are positive constants. The velocity of the particle will

  • decrease with time

  • be independent of α and β

  • drop to zero when α = β

  • increase with time


138.

If A + B = C and that C is perpendicular to A. What is the angle between A and B, if A = B

  • π4 rad

  • π2 rad

  • 3 π4 rad

  • π rad


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139.

A body is whirled in a horizontal circle of radius 25 cm. It has an angular velocity of 13 rad/s. What is its linear velocity at any point on circular path?

  • 2 m/s

  • 3 m/s

  • 3.25 m/s

  • 4.25 m/s


140.

Assertion: If  α =  - 2t for a particle moving in a straight line starting with initial velocity 4 m/s from the origin, then distance travelled by it in 2 s is same as displacement.

Reason: Velocity changes direction after 2 s only.

  • If both assertion and reason are true and reason is the correct explanation of assertion.

  • If both assertion and reason are true but reason is not the correct explanation of assertion.

  • If assertion is true but reason is false.

  • If both assertion and reason are false.


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