Question

Let theta denote the angular displacement of a simple pendulum oscillating in a vertical plane. If the mass of the Bob is m, then the tension in string is

Answer 1

The tension has to hold the part of the weight in the direction of the string:

T = mg*cos(theta)

Theta=0, whole weight, theta=90, T=0, if the pendulum is horizontal, the string will be loose! Yeah

Answer 2

Answer:

So the tension  in the string T =mg cosθ

Explanation:

Now given that

mass of bob = m

Angle from vertical plane =θ

Lets T is the tension in the string

From the diagram

Weight of bob have two component ,first one(mg cosθ) balance the tension in the string and other one(mg sinθ)  make the bob to move in the plane.

So the tension  in the string T =mg cosθ