Question

If a car slows from 60 m/s to 45 m/s in a period of 5.0 s, what was the average acceleration?

Group of answer choices

-60 m/s2

15 m/s2

-45 m/s2

-3 m/s2

Answer 1

To find the average acceleration, you can use the formula:

\[
a = \frac{\Delta v}{\Delta t}
\]

where:
- \( \Delta v \) is the change in velocity,
- \( \Delta t \) is the change in time.

In this case:

- Initial velocity (\( v_i \)) = 60 m/s
- Final velocity (\( v_f \)) = 45 m/s
- Change in time (\( \Delta t \)) = 5.0 s

First, calculate the change in velocity:

\[
\Delta v = v_f - v_i = 45 \, \text{m/s} - 60 \, \text{m/s} = -15 \, \text{m/s}
\]

Now plug this value into the acceleration formula:

\[
a = \frac{\Delta v}{\Delta t} = \frac{-15 \, \text{m/s}}{5.0 \, \text{s}} = -3 \, \text{m/s}^2
\]

Thus, the average acceleration is:

\(-3 \, \text{m/s}^2\)

The correct answer is:

**-3 m/s²**