Question

A trolley is under the action of a constant force $F$. The sand contained by it is poured out through a hole in the floor at the rate of $m$ per second.If initial mass of sand and trolley was $M$ and initial speed was $u$, the acceleration of trolley at time t is given by :

• A. $\frac{F}{M-mt}$
• B. $\frac{F}{M+mt}$
• C. $\frac{F}{M-m}$
• D. $\frac{F}{M+m}$

Answer 1

The correct option is A $\frac{F}{M-mt}$

At any instant t , the mass contained becomes $M-mt$

Hence , $(M-mt)\ast a=F$

which gives $a=\frac{F}{M-mt}$