The change in the centripetal force of a body moving in a circular path , if speed is made half and radius is made 5 times original value , will

Options

A. increase by `(18)/(20)`
B. decreases by `(19)/(20)`
C. decreaseby `(9)/(20)`
D. increase by `(17)/(20)`

Answer

B

Explanation

Centripetal force , F `=(mv^(2))/(r)`
`F_1=(m(v//2)^(2))/(5r)=(mv^(2))/(4)=(mv^(2))/(20)`
`DeltaF=F-F_(1)=(mv^(2))/(r)-(mv^(20))/(20r)=(19)/(20)(mv^(2))/(r)`