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Motion In Straight Line

Question
CBSEENPH11026346
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A block is kept on the floor of an elevator at rest. The elevator starts descending with an acceleration of 12 m/s2. Find the displacement of the block during the first 0.2 s after the start. (Take, g = 10 m/s2)

  • 30 cm

  • zero

  • 20 cm

  • 25 cm

Solution

C.

20 cm

The acceleration (downward) of the elevator is 12 m/s2 which is greater than gravitational acceleration g. So, the block will act as a freely falling body.

From the motion of the block

      s = ut + 12 gt2

          = 0 × t + 12 × 10 × (0.2)2

           = 12 × 10 × 0.2 × 0.2

        s = 20 cm

Some More Questions From Motion in Straight Line Chapter

When an object in motion can be considered as particle or point object?

Can you think of physical phenomena involving the moon in which moon cannot be treated as particle?

A train is crossing the bridge. Can it be taken as a particle?

Can a train be taken a particle? Give an example in support of your answer.

 A particle is moving along curved line in space. Is the motion one dimensional?

State which of the following are examples of one, two or three dimensional motion: 

(a) A kite flying in the sky.

(b) The earth revolving around the sun. 

(c) A train moving along the equator of the earth in clockwise direction. 

(d) Accelerated motion of a particle in a straight line.

Define distance.

Define displacement.

Can magnitude of displacement be greater than distance travelled by particle?

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