A body is falling freely under gravity. The distances covered by

Subject

Physics

Class

JEE Class 12

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 Multiple Choice QuestionsMultiple Choice Questions

1.

The percentage errors in the measurement of length and time period of a simple pendulum are 1% and 2% respectively. Then the maximum error in the measurement of acceleration due to gravity is

  • 8 %

  • 3 %

  • 5 %

  • 6 %


2.

Dimensional formula of Stefan's constant is

  • [MT-3K-4]

  • [MLT-2K-4]

  • [ML2T-2]

  • [MT-2L0]


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3.

A body is falling freely under gravity. The distances covered by the body in first, second and third minute of its motion are in the ratio

  • 1 : 4 : 9

  • 1 : 2 : 3

  • 1 : 3 : 5

  • 1 : 5 : 6


C.

1 : 3 : 5

Distance covered in a particular time is

            sn = u + 12 g 2n - 1    s1 = 0 + 12g 2 × 1 - 1 = g2        s2 = 0 + 12g 2 × 2 - 1 = 32 gand  s3 = 0 + 12g 2 × 3 - 1 = 52 g

Hence, the required ratio is

s1 : s2 : s3 = g2 : 32 g : 52 g                 = 1 : 3 : 5


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4.

A bullet fired into a fixed wooden block loses half of its velocity after penetrating 40 cm. It comes to rest after penetrating a further distance of

  • 223 cm

  • 403 cm

  • 203 cm

  • 225 cm


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5.

A ball A is thrown up vertically with a speed u and at the same instant another ball B is released from a height h. At time t, the speed of A relative to B is 

  • u

  • 2u

  • u − gt

  • u2 - gt


6.

A bullet is to be fired with a speed of 2000 ms-1 to hit a target 200 m away on a level ground. If g = 10 ms-2, the gun should be aimed

  • directly at the target

  • 5 cm below the target

  • 5 cm above the target

  • 2 cm above the target


7.

The resultant of two vectors P and Q is R. If the magnitude of Q is doubled, the new resultant becomes perpendicular to P. Then the magnitude of R is 

  • P + Q

  • Q

  • P

  • P + Q2


8.

A motor car is moving with a speed of 20 ms-1 on a circular track of radius 100 m. If its speed is increasing at the, rate of 3 ms-1, its resultant acceleration is

  • 3 ms-2

  • 5 ms-2

  • 2.5 ms-2

  • 3.5 ms-2


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9.

A stationary body of mass 3 kg explodes into three equal pieces. Two of the pieces fly off in two mutually perpendicular directions, one with a velocity of 3 i^ ms-1 and the other with a velocity of 4 j^ ms-1. If the explosion occurs in 10-4  s, the average force acting on the third piece in newton is

  • 3i^ + 4j^ × 10-4

  • 3i^ - 4j^ × 10-4

  • 3i^ + 4j^ × 104

  • - 3i^ + 4j^ × 104


10.

A mass of 1 kg is just able to slide down the slope of an inclined rough surface when the angle of inclination is 60°. The minimum force necessary to pull the mass up the inclined plane (g = 10 ms-2) is

  • 14.14 N

  • 17.32 N

  • 10 N

  • 16.66 N


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