Question

A simple pendulum of length l and mass m is initially at its lowest position. It is given the minimum horizontal speed necessary after to move in a circular path about the point of suspension. The tension in the string at the lowest positive of the bob is

Answer 1

Given :

Length = l

Mass = m

To find :

The tension in the string when the bob is at lowest position

Solution :

• The radius of the circular path is equal to the length of the road

• In this situation the weight of the bob acts in the vertical downward direction and the tension in the string acts in the opposite direction it.

• velocity of boby = √5gR   =√5gl

• T-mg = mv²/R

        T = mg + m(√5gl)² / R

        T=mg + 5mg

        T = 6mg

• The tension in the string is T=6mg