Question

A particle of mass m performs vertical motion in a circle of radius r . Its potential energy at the highest point is a) 2 mgr b)mgr c) 0 d) 3mgr

Answer 1

Answer : (a) 2mgr
When a particle of mass m perform vertical circular motion of radius r .
Then, potential energy at the highest point is maximum .
we know, potential energy = mg × height of body from Ground level
Here m is mass and g is acceleration due to gravity

h = 2r [ from Ground level ]

So, potential energy = mg × 2r = 2mgr

Answer 2

Solution : option is A: 2mgr

explanation:
mass of particle=m
Radius =r
P.E at highest point.=?
Formula : P.E=mgh
where m is mass 
g= acceleration due to gravity
h= height =2r from ground level.
P.E= mgh
=mgx2r
=2mgr