# Homework Help: Change in velocity, average acceleration

1. Sep 26, 2009

### salaam

1. The problem statement, all variables and given/known data
Earth's orbit around the SUn is nearly circular. THe period is 1 year = 365.25 days. In an elapsed time of 2.70 days, what is earth's angular displacement? what is the change in earth's velocity (perpendicular to the average velocity) What is the earth's average acceleration during 2.7 days? (perpendicular to the average velocity)

2. Relevant equations
a =v/t
v = s/t

3. The attempt at a solution
I have already completed the first question and got 4.64×10-2 rad and it was right.

but the next two i'm having major problems with. and i am so confused. anyone help!

2. Sep 26, 2009

### G01

You know how fast the earth's tangential velocity is (or you can get it using the angular displacement and time).

How does the tangential velocity relate to the centripetal acceleration for uniform circular motion?

3. Sep 27, 2009

### salaam

I'm really not sure.. can you elaborate?

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