Question

At the starting gun a runner accelerates from rest at 1.9 m/s2 for 2.2s. What is the runner’s speed 2s after she starts running?

Answer 1

Answer:

$v_{f}$ = 3.8 m/s

Explanation:

When the runner start the running, she is at rest. So the initial velocity of the runner is zero (0 m/s). And then she accelerates at  a rate of 1.9 m/s² for 2.2 s. But we need to find the final velocity after t = 2 s when she starts the running. So, we take time equal to 2 second.

Given data:

Initial velocity = $v_{i}$ = 0 m/s

Acceleration = a = 1.9 m/s²   (for 2.2 s after starting the race)

Time = t = 2 s

Final velocity = $v_{f}$ = ?

According to the First equation of motion

$v_{f}$ =  $v_{i}$ + at

$v_{f}$ = 0 + (1.9)(2)

$v_{f}$ = 3.8 m/s