# Homework Help: KE-PE Experiment

1. Nov 24, 2004

I have to do an labwork on how to determine experimentally how much of the potential energy of a wooden block is transformed into kinetic energy when it is gliding down an inclined plane.
My question is, how exactly should the experiemnt be conducted in the simpliest way with as few equipment as possible?

2. Nov 24, 2004

### ponjavic

Just an idea, let it glide from the top to (close to) the bottom and calculate the time it takes for it to reach (close to) the bottom mark, this way you will have the velocity in the middle of the two points (since accelleration is constant) Then you have everything but the height which should be easily calculated.
mgh:mv^2/2
now you have v, h can be calculated and g is known, you should be able to get the relationship thus the how much is transformed into kinetic energy (%)

3. Nov 24, 2004

Do you think this method is accurate enough? Shouln't the friction be taken into consideration?

4. Nov 25, 2004

### ponjavic

Depends, what grade are you in, have you worked with friction?
The method definately isn't accurate but it takes little equipment and work, still it wouldn't be too hard to figure out (find) the friction coefficient and then include that in the model...
Then the experiment should be pretty accurate not considering air friction.
Also experiment with different angles on incline to see how this effects the relationship. Maybe the % is higher at a low angle due to lower velocity (lower air resistance) and so on...
All depends on how thorough the experiment should be and what you have learned so far

5. Nov 30, 2004

I conducted the experiment using some kinematic formulas and it turned out that i did not need to know the mass nor the friction.

The result is attached. I hope it is correct since it followed your method.

Thank you for the help!

I am in the 10th grade btw.

#### Attached Files:

• ###### PEKE.doc
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Last edited: Nov 30, 2004
6. Nov 30, 2004

### ponjavic

Yeah then my layout should be good enough I think, I hope your teacher likes it and I hope I didn't ruing the "make something myself" part of the laboration for you =)
Be sure to let us know how the results were so if they weren't good enough we can provide you with more advice!

P.S Just realized how stupid my answer to the role of friction was, since friction is the cause of a relationship between potential and kinetic energy (it does not equal) it should not be included in the model :P

Last edited: Nov 30, 2004