Question

A force acts for 10 sec on a body of mass $100\text{kg}$ after which it ceases. If the body travels $160\text{m}$ in the next 8 sec, find the magnitude of the force.

• A. $100\text{N}$
• B. $200\text{N}$
• C. $300\text{N}$
• D. $400\text{N}$

Answer 1

The correct option is B $200\text{N}$

Let $AB$ be the distance travelled by body when the force was acting and $BC$ be the distance travelled in absence of force.
For $BC:$
Using second equation of motion
$S_{BC}=v_{B}t+\frac{1}{2}a{t}^2$
$\Rightarrow 160=v_B\times 8$ ($\because$ acceleration $=0$)
$\Rightarrow v_B=20\text{m/s}$
For $AB:$
$v_B=u+at$
$20=0+a\times 10$
$\Rightarrow a=2{\text{m/s}}^2$
$\therefore F=ma=100\times 2=200\text{N}$