A cane filled with water is revolved in a vertical circle of radius 4 m and water just does not fall down. The time period of revolution will be –

Options

A. 2 s
B. 4 s
C. 8 s
D. 10 s

Answer

B

Explanation

When a body is revolving in circular motion, it is acted upon by a centripetal force directed towards the centre. Water will not fall if weight is balanced by centripetal force. Therefore,
`mg=(mv^(2))/( r )" "…(i)`
`implies" "v^(2)=rg`
Circumference of a circle is `2pir`.
Time for a revolution `=(2pir)/(v)`
Putting the value of v from Eq. (i),
we get
`T=(2pi r)/(sqrt(gr))=2pi sqrt((r)/(g))`
Given, r = 4 m, g = 9.8 `"ms"^(-2)`
`T=2pi sqrt((4)/(9.8))impliesT=(4pi)/(sqrt(9.8))=4s`