Question

A man applies a constant force of $5\text{N}$ on an object of mass $2\text{kg}$ and displaces it by $5\text{m}$. The object was initially at rest. The final velocity of object is

• A. $10\text{m/s}$
• B. $5\text{m/s}$
• C. $25\text{m/s}$
• D. $15\text{m/s}$

Answer 1

The correct option is B $5\text{m/s}$

Given, force$=5\text{N}$, mass $=2\text{kg}$, displacement $=5\text{m}$ and initial velocity$\left(u\right)=0\text{m/s}$ as object was initially at rest.

Applying Work - Energy theorem,
Net work done $=$ Change in Kinetic energy.

$W=\text{Force}\times \text{Displacement}=\frac{1}{2}m(v^2-u^2)$
$5\times 5=\frac{1}{2}m(v^2-u^2)$ as $(u=0)$
$\Rightarrow 25=\frac{1}{2}\times 2\times \left(v^2\right)$
$v=5\text{m/s}$

Hence option B is the correct answer.