Question

A pendulum bob of mass 100g hangs by a thread l=2m.It is pulled aside by 60° and released.Find the tension when bob is at lowest point.

Answer 1

When Bob is at the lowest point, tension(T) provides the net centripetal force along with Mg:

Mgl(1-cos60°)=(1/2)Mv^2

So v^2=gl

So

T-mgcos60°=mv^2/l

T=1.5N

Comments

But when it is talking about the lowest point. Eqn should be

T-mgcos0 = mv^2/l

T = mg + mv^2/l

T = 2 N