A balloon with mass `m` is descending down with an acceleration a `(where altg)` . How much mass should be removed from it so that it starts moving up with an acceleration a?

Options

A. `(ma)/(g-a)`
B. `(2ma)/(g+a)`
C. `(2ma)/(g-a)`
D. `(ma)/(g+a)`

Answer

B

Explanation

Let `F_(B)rarr" upthrust"`

So `mg-F_(B)=ma" …(i)"`

`F_(B)-(m-Deltam)g=(m-Deltam)a" ….(ii)"`
`(Deltam)g=2ma-Deltama`
`rArr" "Deltam(g+a)=2ma`
`rArr" "Deltam=(2ma)/(g+a)`