Question

A block of mass $m$ is freely sliding down on a smooth inclined plane from its top. The block reaches the bottom of inclined plane and then describes a vertical circle of radius $r$ along smooth track. If vertical height of inclined plane is $3r$, the normal reaction on the block when it is crossing highest point of vertical circle:

• A. $2mg$
• B. $mg$
• C. $\frac{mg}{2}$
• D. $Zero$

Answer 1

The correct option is B $mg$

$ByconservationofEnergy\frac{1}{2}m{v}^2+mg\left(2r\right)=mg\left(3r\right)\Rightarrow v^2=2grN+mg=\frac{m{v}^2}{r}\Rightarrow N=2mg-mg=mg$