Posted by **Sarah** on Sunday, September 10, 2006 at 4:27pm.

An electron had a constant acceleration of +3.2m/s^2. At a certain instant its velocity is +9.6m/s. What is its velocity at a)2.5 s earlier and b )2.5s later?

I will be happy to critique your work.

I could a= change in velocity / change in time ?

Here's the question:

"An electron had a constant acceleration of +3.2m/s^2. At a certain instant its velocity is +9.6m/s. What is its velocity at a)2.5 s earlier and b )2.5s later?"

a=+3.2m/s^2

(1) v(t)=a*t

You should be able to answer the question with (1)

I suppose we're supposed to have the initial velocity =0, but an electron is never at rest.

so the velocity would be -8m/s for part

and 8m/s for part b?

No, I think the question wants you to suppose that t=3 and that the electron has been accelerated from rest. (That's why I said the question is somewhat imaginary. No electrons are at complete rest.)

The equation v=a*t is a line with slope a; t is the independent variable here.

At t = 3 v=a*t=+3.2*3=+9.6

v=a(t+2.5) 2.5s later

v=a(t-2.5) 2.5s earlier

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