Question

An object is moving east, and its velocity changes from 65 m/s to 25 m/s in 10 seconds. Which describes the acceleration?

negative acceleration of 4 m/s2
positive acceleration of 4 m/s2
positive acceleration of 9 m/s2
negative acceleration of 9 m/s2

Answer 1

To determine the acceleration, we can use the formula for acceleration:

\[
a = \frac{{v_f - v_i}}{{t}}
\]

where:
- \( v_f \) is the final velocity,
- \( v_i \) is the initial velocity,
- \( t \) is the time.

In this case:
- \( v_f = 25 \, \text{m/s} \)
- \( v_i = 65 \, \text{m/s} \)
- \( t = 10 \, \text{s} \)

Now, substituting the values into the formula:

\[
a = \frac{{25 \, \text{m/s} - 65 \, \text{m/s}}}{{10 \, \text{s}}}
\]

\[
a = \frac{{-40 \, \text{m/s}}}{{10 \, \text{s}}}
\]

\[
a = -4 \, \text{m/s}^2
\]

Since the acceleration is negative, this indicates that the object is decelerating (slowing down).

Thus, the correct description of the acceleration is **negative acceleration of 4 m/s²**.