Posted by **Bob** on Saturday, September 12, 2009 at 3:32pm.

A car slows down from 23 m/s to rest in a distance of 85m. What is its constant acceleration?

I got -6.224, but a friend was telling me it's -3.11 and that I had to divide by 2. Why is that?

- Physics B -
**drwls**, Saturday, September 12, 2009 at 3:53pm
The average velocity during deceleration is 11.5 m/s. The time required to decelerate is 85/11.5 = 7.39 s

The acceleration rate is -23 m/s/7.39s = -3.11 m/s^2

I added the minus sign because it is decelerating

- Physics B -
**Bob**, Sunday, September 13, 2009 at 10:31am
How did you get the average velocity?

- Physics1 -
**Christina**, Monday, November 4, 2013 at 10:02pm
i think -3.11

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