# Homework Help: Find acceleration given initial and final velocity, and displacement

1. Jul 28, 2013

### donking225

1. An electron in the cathode ray tube of a television set enters a region where it accelerates uniformly from a speed of 62300 m/s to a speed of 3.86 × 106 m/s in a distance of 3.17 cm.
What is its acceleration?

2. a = [Vf2 - Vi2] / [2d]

3. a = [(3.86 × 106)m/s2 - 62300m/s2] / [2 * 0.0317m]

Last edited: Jul 29, 2013
2. Jul 29, 2013

### siddharth23

Acceleration is rate of change of velocity. It's (vf-vi)/t . Don't square the velocities. And don't divide by the distance.

More applicable formula here would be
v^2=u^2 + 2as (s is the distance)

3. Jul 29, 2013

### donking225

Wouldn't you still divide by (2s) anyways based on algebra. To get (a) alone you would subtract u^2 from both sides of the equation and have v^2-u^2= 2as. Then you would divide both sides by (2s) to get (a) alone. Isn't that basically the same as the original equation I had? I'm also confused about what you mean by not squaring the velocities.

Last edited: Jul 29, 2013
4. Jul 29, 2013

### ehild

The result is correct.

ehild

5. Jul 29, 2013

### donking225

That's what I thought too, I guess the only explanation to why I'm getting this wrong on my homework website is that I am entering it in an incorrect format.