Question

A car traveling west in a straight line on a highway decreases its speed from 30.0 meters per second to 23.0 meters per second in 200 seconds. What is the car's average acceleration during this time interval?

Answer 1

`a~~-0.04"m/s"^2"`

Explanation:

Acceleration is the change in velocity over the time interval. The equation to use is `v_f=v_i+at`, where, in SI units, `v_f` is final velocity in m/s, `v_i` is initial velocity in m/s, `a` is average acceleration in `"m/s"^2"`, and `t` is time in s.

Given
`v_i="30.0 m/s"`
`v_f"23.0 m/s"`
`t="200 s"`

Unknown
`a`

Solution
Rearrange the equation to isolate `a`, substitute the given values into the equation and solve.

`v_f=v_i+at`

`a=(v_f-v_i)/t`

`a=(23.0"m/s"-30.0"m/s")/(200"s")`

`a=(-7.00"m/s")/(200"s")~~-0.04"m/s"^2"`

(rounded to one significant figure due to `"200 s"`)