An iron sphere of mass `20xx10^-3`kg falls through a viscous liquid with terminal velocity 0.5 `ms^(-1)` The terminal velocity (in `ms^-1`) of another iron sphere of mass `54 xx 10^2` kg is

Options

A. 4.5
B. 3.5
C. 2.5
D. 1.5

Answer

A

Explanation

Terminal velocity, `V_(10 propto r^(2)`
`V_(n)/V_(12) = [r_(1)/r_(2)]^(2)= [[r_(1)/r_(2)]^(3)]^(2//3)`
`0.5/V_(12) = [M_(1)/M_(2)]^(2//3) =[(20xx10^(-3))/(54xx10^(-2))]`
`therefore V_(120=4.5m//s`