Help, New Physics Student!

1. Jan 24, 2008

ocigano

I am new to Physics and I need help on this problem

A skater increases her speed uniformly from 2.0 meters per second to 7.0 meters per second over a distance of 12 meters. The magnitude of her acceleration as she travels this 12 meters is?

A. 2.4 m/s squared
B. 3.8 m/s squared
C. 1.9 m/s squared
D. 2.2 m/s squared

Can you please give me an explanation of how to solve this since this seems pretty easy?

thanks

2. Jan 24, 2008

hage567

You must show some work in order to get help. Do you know your kinematic equations? You only need one equation to solve this. Can you explain what is confusing you?

3. Jan 24, 2008

ocigano

My teacher taught me a=v/t and I get the answer A but it says that I am wrong. But I don't have the T so I don't know what to do from then on.

4. Jan 24, 2008

hage567

I'm sure there are derivations of some other useful kinematic equations in your textbook (if you were given one). But what you can do is start with the definition of average acceleration

$$a_{ave} = \frac{\Delta v}{\Delta t}$$

The displacement (distance) of the car will be the average velocity of the car multplied by the time interval $$\Delta t$$

So that is $$\Delta x = (\frac{v_o + v}{2}) \Delta t$$

So arrange this for $$\Delta t$$ and substituting it into your first equation will allow you to solve for a in terms of displacement.

Does that make sense?

See https://www.physicsforums.com/showpost.php?p=905663&postcount=2

This site might help: http://hyperphysics.phy-astr.gsu.edu/hbase/mot.html#mot1