Question

The graph describes an airplane's acceleration $\left(a\right)$-time $\left(t\right)$ during its take-off run. The airplane's velocity when it lifts off at $t=20s$ is.

• A. $40m{s}^{-1}$
• B. $50m{s}^{-1}$
• C. $90m{s}^{-1}$
• D. $180m{s}^{-1}$

Answer 1

Answer: (C)

$90m{s}^{-1}$

$a=\frac{dv}{dt}$ or $v=\int adt$
Thus$,v$ is equal to area under $a-t$ curve.
Thus, here, we have, at $t=20,v=\frac{1}{2}\times (3+5)\left(10\right)+5.10=90m/s$