Question

Question #85a19

Answer 1

For circular motion of a body of mass `m` moving with velocity `v` in a circle of radius `r`, centripetal force is given by the expression
`F_c=(mv^2)/r`

Using the centrifugal force conditions, the tension in the string at the top of path can be written as
`T_"top"=(mv^2)/r-mg`
where `g=9.81ms^-2` is acceleration due to gravity.

Inserting given values we get
`4.0=(0.30v^2)/0.7-0.30xx9.81`
Rearranging we get
`(0.30v^2)/0.7=4.0+0.30xx9.81`
`=>v=4.0ms^-1`, rounded to one decimal place.