A flywheel of moment of inertia 0.4 kg-m2 and radius 20 cm is fre

Subject

Physics

Class

NEET Class 12

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 Multiple Choice QuestionsMultiple Choice Questions

1.

If P and Q are two non-collinear unit vectors and if P + Q = 3 then the value of (P - Q)(2P + Q) will be

  • 1

  • 2

  • 12

  • 32


2.

A gas bubble forms an explosion under water which oscillate with a period T ∝ paρbEc, where p is the static pressure, ρ is the density ofwater and E is the total energy of explosion. Then, the values of a, b and c will be

  • - 56, 12, 13

  • 25, 13, 14

  • 45, 98, 12

  • 32, 14, 56


3.

If a particle moves a distance x at a speed v1 and comes back with speed v2 , then the average speed and average velocity during this round trip will respectively be

  • 0, v1 + v2

  • 2v1v2v1 + v2, 0

  • v1 + v2, 0

  • v1 − v22v1v2v1 + v2 


4.

On an electron in an atom both electric and gravitational forces are collinear we neglect gravitational force (FG) in comparision to electric force (FE ), because

  • FE > FG

  • FN > FE

  • FE >> FG

  • FN >> FG


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5.

A metal block of mass 1 kg is resting on a frictionless horizontal plane. It is struck by a jet releasing water at a rate of 1 m/s and at a speed of 4 m/s. Then, the initial acceleration of the block will be

  • 2 m/s2

  • 8 m/s2

  • 1 m/s2

  • 4 m/s2


6.

A body of mass 5 kg moves on a straight path as a function of time x = t3 − 12t. The force on the body at t = 5s will be

  • 100 N

  • 150 N

  • 120 N

  • 130 N


7.

The potential energy of a certain spring when stretched through a distance x is 20 J. The amoµnt of work that must be done on this spring to stretch it through an additional distance x2 will be

  • 20 J

  • 25 J

  • 5 J

  • 15 J


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8.

A flywheel of moment of inertia 0.4 kg-m2 and radius 20 cm is free to rotate about a central axis. If a string is wrapped on its circumference and it is pulled with a force of 10 N, then the change in its angular velocity after 4 s will be

  • 10 rad/s

  • 20 rad/s

  • 40 rad/s

  • 5 rad/s


B.

20 rad/s

As the string pulls the wheel, then torque is given by

                   ζ = F × r =  = I ω2 - ω1t  ω2 - ω1 = F × r × tI                      = 10 × 0.2 × 40.4           ω = 20 rad/s


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9.

Three identical spheres of mass m each are placed at the corners of an equilateral triangle of side 1 m. Taking one of the corners as the origin, the position vector of centre of mass is

  • 12i + 32 j

  • 12 i + 123 j

  • i + j

  • 2i - j


10.

The driver of a truck travelling with a velocity v suddenly notice a brick wall infront of him at a distance r. How the driver avoid himself by crashing into the wall ?

  • By speeding up the truck

  • By applying a brake

  • By slowing down the truck

  • By taking a circular turn


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