A particle tied with a string is whirled along a vertcial circle.

Options

A. Acceleration of particle is always directed towards centre
B. Acceleration is directed along vertically downard when particle is at lowest position
C. Acceleration at highest point cannot be less than g.
D. Acceleration is greater then 'g' where string is horizontal

Answer

C, D

Explanation

(A) Acceleration has two components. One towards centre known as centripetal acceleration and the other is along tangential direction known as tangential acceleration.
(B) At lowest position acceleration is towards centre, i.e. along vertically upwards direction.
(C ) `T + mg = ma_(c)`
`a_(c ) = (T)/(m) + g`
so `a_(c ) ge g` as `T ge 0`
`T = ma_(c )`
`a_(c ) = T//m` ....(1)
`a_("tang.") = (mg)/(m) = g`
`a_("total") = sqrt((a_(c ))^(2) + (a_(tan g.))^(2)) gt g`