Question

A body of $5kg$ mass is raised vertically to a height of $10m$ by a force of $120N$. Find the final velocity of the body :

• A. $\sqrt{280}m/s$
• B. $\sqrt{200}m/s$
• C. $20m/s$
• D. $Noneofthese$

Answer 1

The correct option is A $\sqrt{280}m/s$

Work done by the force is $W=F\times h=120\times 10=1200J$

out of which $mgh$ will be $lost$ against the $gravity$ or in other words $mgh=5\times 9.8\times 10=490J$ will be $converted$

into $PE$ so the remaining energy for kinetic energy will be $KE=1200-490=710J$

but KE is $\frac{1}{2}m{v}^2$

so the velocity can be calculated as $v=\sqrt{\frac{2KE}{m}}=\sqrt{282}m/s$