# Homework Help: Finding acceleration.

1. Sep 23, 2006

### pieman396

I can not figure out how to do this problem. Can anyone tell me?

A body moving on the x-axis with a constant acceleration increases its x-coordinate by 80m in a time period of 5.0s and has a velocity of +20m/s at the end of this time. Determine the acceleration of the body during this time.

Thanks much!

2. Sep 23, 2006

Which is the equation which expresses the displacement of a body moving on a line with constant acceleration?

3. Sep 23, 2006

### pieman396

is it Vi - Vo / time?

4. Sep 23, 2006

### big man

The hint they give you in the question is that it is constant acceleration.
So you can use you constant acceleration equations of motion.

Type "constant acceleration +equations of motion" into google to learn a bit more about it.

Given you know these variables:

vf=20 m/s
t= 5s
x-xi = 80 m

You can decide which of the standard constant acceleration equations of motion you need to use to solve the problem.

5. Sep 23, 2006

### pieman396

im getting 4m/s^-2

6. Sep 23, 2006

### big man

No that's not right.

http://www.ac.wwu.edu/~vawter/PhysicsNet/Topics/Kinematics/ConstantAccEqMotion.html [Broken]

From your question I can see that you'd need to use three of those equations.

One equation to find the average velocity.
One equation to solve for the initial velocity.
Then one equation to solve for the acceleration.

average velocity = distance/time

v with a bar over the top of it is average velocity so just look on that page to find the equation relating the average velocity, final velocity and initial velocity so you can solve for the inital velocity.

Then you just need to find the remaining equation that uses all your known variables to solve for the unknown acceleration.

Last edited by a moderator: May 2, 2017