A ring starts to roll down the inclined plane of height h without

Subject

Physics

Class

JEE Class 12

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 Multiple Choice QuestionsMultiple Choice Questions

11.

A bridge is in the form of a semi-circle of radius 40 m. The greatest speed with which a motor cycle can cross the bridge without leaving the ground at the highest point is (g =10 ms-2) (Frictional force is negligibly small)

  • 40 ms-1

  • 20 ms-1

  • 30 ms-1

  • 15 ms-1


12.

A ball of mass m is dropped from a height h on a platform fixed at the top of a vertical spring, as shown in figure. The platform is depressed by a distance x. Then the spring constant is

  • mgh + x

  • mgh + 2x

  • 2mg h + xx2

  • mg2h + x


13.

A ball dropped from a height of 2 m rebounds to a height of 1.5 m after hitting the ground. Then the percentage of energy lost is

  • 25

  • 30

  • 50

  • 100


14.

A particle of mass m is moving in a horizontal circle of radius r, under a centripetal force F = kr2, where k is a constant.

  • The potential energy of the particle is zero

  • The potential energy of the particle is kr

  • The total energy of the particle is -k2r

  • The kinetic energy of the particle is - kr


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15.

A ring starts to roll down the inclined plane of height h without slipping. The velocity with which it reaches the ground is

  • 1Ugh7

  • 4gh7

  • gh

  • 2gh


C.

gh

For a ring, k2 = r2 then

                v2 = 2gh1 + k2/r2 = 2gh2 = gh v = gh


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16.

The angular momentum of a particle describing uniform circular motion is L. If its kinetic energy is halved and angular velocity doubled, its new angular momentum is

  • 4 L

  • L4

  • L2

  • 2 L


17.

Two masses m1 = 1 kg and m2 = 2 kg are connected by a light inextensible string and suspended by means of a weightless pulley as shown in the figure.

                

Assuming that both the masses start from rest, the distance travelled by the centre of mass in 2s is (Take g = 10 ms-2)

  • 209 m

  • 409 m

  • 23 m

  • 13 m


18.

A satellite is launched into a circular orbit of radius R around the earth. A second satellite is launched into an orbit of radius 4R. The ratio of their respective periods is

  • 4 : 1

  • 1 : 8

  • 8 : 1

  • 1 : 4


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19.

A body is projected with a velocity of 2 x 11.2 kms-1 from the surface of earth. The velocity of the body when it escapes the gravitational pull of earth is

  • 3 × 11.2 kms-1

  • 11.2 kms-1

  • 2 × 11.2 kms-1

  • 6.5 × 11.2 kms-1


20.

The average depth of Indian ocean is about 3000 m. The fractional compression, VV of water at the bottom of the ocean (given that the bulk modulus of the water = 2.2 × 102 Nm-2 and g = 10 ms-2) is

  • 0.82 %

  • 0.91 %

  • 1.36 %

  • 1.24 %


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