Q. 145.0( 9 Votes )

A pendulum bob of mass 50 g is suspended from the ceiling of an elevator. Find the tension in the string if the elevator (a) goes up with acceleration 1.2 m/s2, (b) goes up with deceleration 12 m/s2, (c) goes up with uniform velocity, (d) goes down with acceleration 1.2 m/s2, (e) goes down with deceleration 1.2 m/s2 and (f) goes down with uniform velocity.

Answer :

Given: mass of the bob = 50g = 0.05 kg


When the elevator is at rest the tension in the string weight of the bob


a) When it goes up with an acceleration in upward direction a pseudo force acts on the bob in downward direction.


The tension in the string becomes=



b) When it goes up with a deceleration in upward direction a pseudo force acts on the bob in downward direction with negative sign.


The tension in the string becomes=s=



c) When it goes up with a uniform velocity in upward direction no pseudo force acts on the bob in downward direction.


The tension in the string becomes=s=



d) When it goes down with an acceleration in downward direction a pseudo force acts on the bob in upward direction.


The tension in the string becomes=s=



e) When it goes down with a deceleration in downward direction a pseudo force acts on the bob in upnward direction with negative sign.


The tension in the string becomes=s=



f) When it goes up with uniform velocity in downward direction no pseudo force.


The tension in the string becomes=



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