An object moves counter`-`clockwise along the circular path shown below. As it moves along the path its acceleration vector continuously points towards point `S`. The object

Options

A. speeds up at `P,Q` and `R`
B. shows down at `P,Q` and `R`
C. speeds up at `P` and shown down `R`
D. shows down at `P` and speeds up at `R`

Answer

C

Explanation

`vec(a).vec(v)=(+)` at P (speeds up)
`vec(a).vec(v)=(-)` at R (speeds down)
`vec(a).vec(v)=(-)` Zero at Q (`a_(t)=0`)