Final answer:
The acceleration of the runner who speeds up from 5 m/s to 9 m/s in 4 seconds is 1 m/s². To calculate this acceleration, we subtract the initial velocity from the final velocity and divide the result by the time taken for this change in speed.
Step-by-step explanation:
To find the acceleration of a runner who speeds up from 5 m/s to 9 m/s in 4 seconds, we can use the formula for acceleration (a), which is:
a = Δv / Δt
where:
- Δv is the change in velocity (final velocity - initial velocity)
- Δt is the change in time (time taken to change velocity)
In this case, the final velocity (vf) is 9 m/s, the initial velocity (vi) is 5 m/s, and the time taken (Δt) is 4 seconds.
Therefore, the acceleration is calculated as follows:
a = (9 m/s - 5 m/s) / 4 s
a = 4 m/s2 / 4 s = 1 m/s2
The runner's acceleration in this part of the race is 1 m/s2.