Can someone explain how this answer was obtained

Question

anonymous · Answer

Im wondering how they got the answer to part b

mrnood · Answer

This is not a static problem - i.e. the forces are not in equilibrium

The tension to support the mass = mg

The tension to produce the circular acceleration = mV^2/r

So total tension 
T = m(g +(v^2/r))

This evaluates to your answer

anonymous · Answer

how did they get the answer to (a)? :/

mrnood · Answer

It says it is held horizontal.

Therefore you know that it is 2.19 m above the bottom position when released.

The loss of potential energy in falling to the bottom =mgh
The gain of kinetic energy in the same path = 0.5 mv^2

These are equal so:

mgh = 0.5mv^2 

so v = sqrt(2gh)

anonymous · Answer

oh ...thanks :)

anonymous · Answer

What does r stand for @MrNood

mrnood · Answer

sqrt = 'squareroot'