Question

A body of mass $5kg$ is raised vertically to a height of $10m$ by a force of $170N$. The velocity of the body at this height will be

• A. 15 m/s
• B. 37 m/s
• C. 9.8 m/s
• D. 22 m/s.

Answer 1

Answer: (D)

Given: Mass of body $(m)=5kg$ ; Height of the body $(h)=10m$ and force $(F)=170N.$
We know that work done by the force $=F\times h=170\times 10=1700J$ and potential energy $=mgh=5\times 10\times 10=500J$.
Now kinetic energy of the body (K.E.) $=1700-500=1200J.$
Therefore if the velocity of the body is v, then kinetic energy $1200=\frac{1}{2}m{v}^2=\frac{1}{2}\times 5\times v^2$ or
$v^2=\frac{1200\times 2}{5}=480$ or $v=\sqrt{480}\cong 22m/s$.