The angle between velocity and acceleration of a particle describ

Subject

Physics

Class

JEE Class 12

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 Multiple Choice QuestionsMultiple Choice Questions

1.

A car moving with a velocity of 20 ms-1 stopped at a distance of 40 m. If the same car is travelling at double the velocity, the distance travelled by it for same retardation is

  • 320 m

  • 1280 m

  • 160 m

  • 640 m


2.

A substance of mass 49.53 g occupies 1.5 cm3 of volume. The density of the substance (in g cm-3) with correct number of significant figures is

  • 3.3

  • 3300

  • 3302

  • 33.0


3.

Two balls are thrown simultaneously in air. The acceleration of the centre of mass of the two balls when in air

  • is equal to g (acceleration due to gravity)

  • depends on the speeds of the two balls

  • depends on the masses of the two balls

  • depends on the direction of motion of the two balls


4.

A body of the mass 50 kg is suspended using a spring balance inside a lift at rest. If the lift starts falling freely, the reading of the spring balance is

  • < 50 kg

  • = 50 kg

  • > 50 kg

  • = 0


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5.

The S.I. unit of specific heat capacity is

  • JK-1

  • J kg-1

  • J mol-1 K-1

  • J kg-1 K-1


6.

The value of acceleration due to gravity at a depth of 1600 km is equal to

  • 4.9 ms-2

  • 9.8 ms-2

  • 7.35 ms-2

  • 19.6 ms-2


7.

A motor pump lifts 6 tonnes of water from a well of depth 25 m to the first floor of height 35 m from the ground floor in 20 minutes. The power of the pump (in kW) is [g = 10 ms-2]

  • 3

  • 12

  • 15

  • 6


8.

If A = 2i^ + 3j^ + 8k^ is perpendicular to B = 4j^ - 4i^ + αk^, then the value of α is

  • - 12

  • 12

  • 1

  • − 1


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9.

The angle between velocity and acceleration of a particle describing uniform circular motion is

  • 180°

  • 90°

  • 45°

  • 60°


B.

90°

When an object follows a circular path at a constant speed, the motion of object is called uniform circular motion. Although the speed does not vary the particle is accelerating because the velocity changes its direction at every point on circular track.

                

The acceleraton is centripetal, which is perpendicular to motion at every point and acts along the radius and directed towards the centre of the curved circular path.


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10.

For which combination of working temperatures, the efficiency of engine is the least ?

  • 100 K, 80 K

  • 40 K, 20 K

  • 80 K, 60 K

  • 60 K, 40 K


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