Question:
An empty plastic box of mass $m$ is found to accelerate up at the rate of $g / 6$ when placed deep inside water. How much sand should be put inside the box so that it may accelerate down at the rate of $g$ / 6 ?
Solution:
$\frac{m g}{6}=-(m g-B)$
$(m+\propto) \frac{g}{6}=(m+\propto) g-B$
B force is constant
$\frac{m g}{6}+m g=(\mathrm{m}+\propto) g-(\mathrm{m}+\propto) \frac{g}{6}$
$=>\frac{m g}{6}+m g=m g+\propto g-\frac{\mathrm{mg}}{6}-\frac{\propto g}{6}$
$\Rightarrow 2 \frac{m g}{6}=\frac{5 \propto g}{6}$
$\alpha=\frac{2 m}{5}$
Click here to get exam-ready with eSaral
For making your preparation journey smoother of JEE, NEET and Class 8 to 10, grab our app now.