If the velocity of light c, gravitational constant G and Planck s

Subject

Physics

Class

JEE Class 12

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 Multiple Choice QuestionsMultiple Choice Questions

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1.

If the velocity of light c, gravitational constant G and Planck's constant h are chosen as fundamental units, the dimensions of length L in the new system is

  • [h1c1G-1]

  • [h1/2c1/2G-1/2]

  • [h1c-3G1]

  • [h1/2c-3/2G1/2]


D.

[h1/2c-3/2G1/2]

Let  L = [hacbGd]

∴  [L'] = [ML2T-1]a [LT-1]b [M-1L3T-2]c

⇒    a = 12 , b = - 32 , d = 12

Hence, L = [h1/2c-3/2G1/2]


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2.

A plate has a length 5 ± 0.1 cm and breadth 2 ± 0.01 cm. Then the area of the plate is

  • 10 ± 0.1 cm2

  • 10 ± 0.01 cm2

  • 10 ± 0.001 cm2

  • 10 ± 1 cm2


3.

A ball hangs from a string inside a train moving along a horizontal straight track. The string is observed to incline towards the rear of the train making a constant small angle with the vertical. It shows that the train is

  • moving with a uniform acceleration

  • moving with a uniform velocity

  • moving with a uniform retardation

  • moving with an acceleration which is increasing uniformly


4.

A particle moves along Y-axis in such a way that its y-coordinate varies with time t according to the relation y = 3 + 5t2 + 7t2. The initial velocity and acceleration of the particle are respectively

  • 14 ms-1 , − 5 ms-2

  • 19 ms-1 , − 9 ms-2

  • 5 ms-1 , 14 ms-2

  • 3 ms-1 , − 5 ms-2


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5.

An object travels north with a velocity of 10 ms-1 and then speeds up to a velocity of 25 ms-1 in 5 s. The acceleration of the object in these 5 s is

  • 3 ms-1 in north direction

  • 3 ms-2 in north direction

  • 15 ms-2 in north direction

  • 3 ms-2 in south direction


6.

An automobile in travelling at 50 km/h, can be stopped at a distance of 40 m by applying brakes. If the same automobile is travelling at 90 km/h, all other conditions remaining same and assuming no skidding, the minimum stopping distance in metres is

  • 72

  • 92.5

  • 102.6

  • 129.6


7.

A rifle shoots a bullet with a muzzle velocity of 500 ms-1 at a small target 50 m away. To hit the target the rifle must be aimed (take g = 10 ms-2)

  • exactly at the target

  • 10 cm below the target

  • 5 cm above the target

  • 5 cm below the target


8.

The centripetal acceleration of particle of mass m moving with a velocity v in a circular orbit of radius r is

  • v2/r  along the radius, towards the centre 

  • v2/r along the radius, away from the centre 

  • mv2/r  along the radius, away from the centre 

  • mv2/r  along the radius, towards the centre 


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9.

An α-particle of mass m suffers one dimensional elastic collision with a nucleus of unknown mass. After the collision the α-particle is scattered directly backwards losing 75% of its kinetic energy. Then the mass of the nucleus is

  • m

  • 2m

  • 3m

  • 32 m


10.

While driving a car around a curve of 200 m radius, the driver notices that a simple pendulum hung to the roof of the car is making an angle of 15° to the horizontal. The speed of the car in km/h is

  • 60.5 

  • 72.5

  • 82.5

  • 92.5


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