An airplane reaches its takeoff speed of 60 m/s in 30 s starting from rest. The time it spends in going from 40 m/s to 60 m/s is
A) 10 s.
B) 15 s.
C) 20 s.
D) 25 s.

Question

Quizplus · Accepted Answer

The airplane accelerates uniformly from 0 to 60 m/s in 30 seconds, so its acceleration is $60 \, \text{m/s} / 30 \, \text{s} = 2 \, \text{m/s}^2$. To find the time to accelerate from 40 m/s to 60 m/s, use the formula $v = u + at$, where $v$ is the final velocity (60 m/s), $u$ is the initial velocity (40 m/s), $a$ is the acceleration (2 m/s$^2$), and $t$ is the time. Solving for $t$, we get $t = (v - u) / a = (60 - 40) / 2 = 20 / 2 = 10$ seconds.

An Airplane Reaches Its Takeoff Speed of 60 M/s in 30