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There is a pendulum in a lift and the lift is coming downwards freely then the time period is :

There is a pendulum in a lift and the lift is coming downwards freely then the time period is : Correct Answer <p>infinity</p>

CONCEPT:

  • Simple pendulum: A point mass attached to a light inextensible string and suspended from fixed support is called a simple pendulum.
    • The vertical line passing through the fixed support is the mean position of a simple pendulum.
    • The vertical distance between the point of suspension and the center of mass of the suspended body (when it is in mean position) is called the length of the simple pendulum denoted by L.

The time period for simple pendulum:

T = 2π √L/g

where, T = time period (sec), L = length of pendulum, g = acceleration due to gravity (m/s2).

  • Acceleration due to gravity (g): It is the acceleration gained by an object due to gravitational force. Its SI unit is m/s2.
    • It has both magnitude and direction, hence, it’s a vector quantity.
    • Acceleration due to gravity is represented by g.
    • The standard value of g on the surface of the earth at sea level is 9.8 m/s2.

EXPLANATION:

  • During free fall the body feels weightlessness inside the lift. Hence g = 0. 
  • As per the above discussion, it's clear that the time period

T = 2π √L/g

 During free fall the body feels weightlessness inside the lift. Hence g = 0.

So time period T = 2π√(L/0)= ∞ 

The correct option is ∞ .

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