# Speed, change in velocity, and average acceleration

1. Aug 30, 2011

### Debbie-Marie

1. The problem statement, all variables and given/known data
At t = 0, an automobile traveling north begins to make a turn. It follows one-quarter of the arc of a circle of radius 10.5 m until, at t = 1.42 s, it is traveling east. The car does not alter its speed during the turn.
Find the car's speed.
Find the change in it's velocity during the turn
Find it's average acceleration during the turn

2. Relevant equations
Speed- m/s
Change of velocity

3. The attempt at a solution
When I first read this problem, the first thing I did was draw a circle. With the circle, I made a 1/4th arc and separated into segments with 10.5 m. Then I outlined the whole arc's time would be 1.42 seconds. So I added the 4 segments and divided them by 1.42 to get the speed. Didn't work. The other questions fall into getting this one. Help would be appreciated!

Last edited: Aug 30, 2011
2. Aug 30, 2011

### collinsmark

Hello Debbie-Marie,

Welcome to Physics Forums!
I'm not quite sure I follow you methods. The problem might be in adding the 4 segments together before dividing by the time. But I'm not quite sure what you meant though.

Let's start over. You already know the time it takes to travel one quarter of the way around the circle. So the first order of business is to find the distance equal to one quarter of the way around the circle. Perhaps, ask yourself these questions.

If you know the radius of a circle, what is the entire circumference of the circle?

So, if you know the radius of a circle, what is 1/4 the distance around that circle?

From there, you should be able to calculate the speed and such.

(also, you should show us your calculations in the future.)

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