What is Johnny's acceleration if his speed increases from 5 m/s to 25 m/s over 5 seconds?

To determine Johnny's acceleration, we can use the formula for acceleration, which is defined as the change in velocity over the time taken for that change. The formula can be expressed as:

[ \text{Acceleration} (a) = \frac{\text{Final Velocity} (v_f) - \text{Initial Velocity} (v_i)}{\text{Time} (t)} ]

In this scenario, Johnny's initial speed is 5 m/s and his final speed is 25 m/s, with the time interval being 5 seconds.

First, we calculate the change in velocity:

[ v_f - v_i = 25 , \text{m/s} - 5 , \text{m/s} = 20 , \text{m/s} ]

Next, we substitute the values into the acceleration formula:

[ a = \frac{20 , \text{m/s}}{5 , \text{s}} = 4 , \text{m/s}^2 ]

Thus, the calculated acceleration is 4 m/s², making it clear why this value is the correct answer. This means that Johnny's speed increases by 4 meters per second for every second