A small block of mass m moving on a smooth track connected with a circular track of radius R. If it starts from rest at P, what is the resultant force acting on it at Q

At Q velocity of block, v,
1/2mv^2 = mg(5R-R)
v^2 = 8gR
now, forces acting on the block are,
mg downwards and mv^2/R to the right
therefore resultant F = under root[(mg)^2 + (8mg)^2]
    = under root[65(mg)^2]
    = root[65] mg
sorry, dont hve the symbol for under root.