A small block of mass `1` kg is a circular are of ratius `40` m . The block sides along the track without topping and a frictionnal force acts on it in the direction opposite in the instrmens velocity . The work done in evercoming the friction up to the point `Q` as shown is the figure below is `150 J`
(Take the acceleration due to gravity `g = 10 ms^(-2))`
The magnitude of the normal reaction that acts on the block at the point `Q` is
