Ablock of mass m is released from rest at a height r above a horizontal surface. the acceleration due to gravity is g. the block slides along the inside of a frictionless circular hoop of radius r. which one of the following expressions gives the speed of the block at the bottom of the hoop?

Explanation:

Given that

Mass = m

Height h=R

acceleration due to gravity = g m/s²

Initially the speed of the mass ,u=0  m/s

The final speed of the mass at bottom = v m/s

Now from work power energy theorem

Work done by all forces=Change in the kinetic energy

Given that surface is friction less that is why work done by the friction force is zero.

Therefore the speed at the bottom of the circular loop is

see earlier

+15-35=-20

going in opposite directions