a train starts from a resting position and reaches 21 m/s in 7 seconds. what is the trains…

Explanation:

Step1: Identify acceleration formula

The formula for acceleration is $a=\frac{v - u}{t}$, where $v$ is final velocity, $u$ is initial velocity and $t$ is time.

Step2: Determine initial and final velocities and time

The train starts from rest, so $u = 0\ m/s$, $v=21\ m/s$ and $t = 7\ s$.

Step3: Substitute values into formula

$a=\frac{21 - 0}{7}=\frac{21}{7}=3\ m/s^{2}$

Answer:

3 m/s² (corresponding to the option that should be $3\ m/s^{2}$ which seems to be a mis - typed $3m\ ^\wedge2$ in the options)