An object falling through a fluid is observed to have acceleration given by ` a= g- bv` where ` g= gravitational acceleration and (b) is constant. After a long time of rlease. It is observed to fall with constant speed. What must be the value of constant speed ?

Explanation

When speed becomes constant accleration `a = (dv)/(dt) = 0`
Give acceleration `a = g - bv`
where, `g =` gravitional accleration
Clearly, from above equation as speed incrases accleration will decrease. At a certain speed say `v_(0)`, acceleration will be zero and speed will remain constant.
Hence `a = g - bv_(0) = 0`
`rArr v_(0) = g//b`