Question

Eight spherical rain drops of the same mass and radius are falling down with a terminal speed of `6cms^(-1)`. If they coalesce to form one big drop, what will be its terminal speed? Neglect the buoyancy due to air
A. `1.5 cms^(-1)`
B. `6 cms^(-1)`
C. `24 cms^(-1)`
D. `32 cms^(-1)`

Answer 1

Correct Answer - C
Equanting the volume, we have
`8((4)/(3) pir^(3))=(4)/(3) piR^(3)` or, `R=2r`
`v_(T )prop (radius^(2))`
Radius has become two times. Therefore, terminal velocity will become 4 times.