Question

The position-time graph of a body of mass $2\text{kg}$ is as given in figure. What is the impulse on the body at $t=4\text{s}$?

• A. $2/3\text{kg m/s}$
• B. $-2/3\text{kg m/s}$
• C. $3/2\text{kg m/s}$
• D. $-3/2\text{kg m/s}$

Answer 1

The correct option is D $-3/2\text{kg m/s}$

At $t=4\text{s}$, the body has constant velocity $u=\frac{3}{4}{\text{ms}}^{-1}$
After $t=4\text{s}$, the body is at rest, as $\frac{dx}{dt}=0\Rightarrow v=0$
Impulse $=m(v-u)=2\text{kg}(0-3/4{\text{ms}}^{-1})=-\frac{3}{2}{\text{kg ms}}^{-1}$