A ball moves along a curved path of radius 5m as shown in figure. It starts from point A and reaches the point B. Calculate the normal force that acts on the ball at B, assuming that there is no friction between the ball and the surface of contact.

Explanation

As is clear from figure,
P.E. of ball at `A=K.E.` of ball at B
`mgh=(1)/(2)mv^(2)`
`v^(2)=2gh=2gr`
centripetal force on the ball at B
`f=(mv^(2))/(r)=(m)/(r)(2gr)=2mg` If R is normal force of reaction acting on the ball in the upward direction at B, then `f=R-W or R=f+W=2mg+mg=3mg`