A particle is given an initial speed u inside a smooth spherical shell of radius $R=1m$ that it is just able to complete the circle. Acceleration of the particle when its velocity is vertical is

Question

$$(a)\;g \sqrt {10} \quad (b)\;g \quad (c)\;g \sqrt 2 \quad (d)\;g \sqrt 6$$

Comments

2g is not equal to g√10...