MCQ
The acceleration-time graph for a particle moving along $x$-axis is shown in figure. If the initial velocity of particle is $-5 \,m / s$, the velocity at $t=8 \,s$ is ....... $m / s$
- ✓$+15$
- B$+20$
- C$-15$
- D$-20$
The area under $a-t$ graph gives change in velocity.
Given, $u=-5 \,m / s$
$\Rightarrow$ Area on positive side $=\frac{1}{2} \times 6 \times 10=30 \,ms ^{-1}$
$\Rightarrow$ Area on negative side $=\frac{1}{2} \times 2 \times 10=10 \,ms ^{-1}$
Net area $=30-10=20 \,ms ^{-1}$
$\Delta v=$ Area
$v-(-5)=20$
$\Rightarrow v=15 \,ms ^{-1}$
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