# Conservation of Energy error

## Homework Statement

We did an experiment where A marble travels down a ramp,
rolls along for 5 cm, then falls off a desk. The marble starts off
while gravitational potencial energy, and ends with kinetic energy.
We were given a formula for the distance from the desk the marble
lands, 'x', calculated by multiplying the height of the ramp by the
height the desk and square rooting the product. So here's my question:
Why is the expected 'X' so different from the 'X' obtained in the experiment?

Egpe = mgh
Eke = 1/2mv**2

## The Attempt at a Solution

Is the large percent error caused by the marble
having some kinetic energy on the ramp?
HELP!

Jen DM

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Shooting Star
Homework Helper
The formula for dist from the desk should be 2*sqrt(height of ramp*height of table), assuming no loss in energy for the 5 cm roll. You can deduce it quite easily.

I know that that formula shows what should happen, but the results of the experiment show something 30% different, and I was wondering why they are so different, i(e sound energy present?)

Thanks

Shooting Star
Homework Helper
Your original formula didn't have the factor of 2. So, I thought that could be the reason for the discrepancy.

The marble also has rolling KE, which it gains when it crosses the flat table, which should be the most significant factor. The formula deduced was for just a point mass sliding.

Sound is emitted after the marble strikes the ground and is not relevant, unless of course you mean the sound when it hits the table and rolls across it. That should be very less.

That makes sense, since the marble is rolling, not sliding down the ramp.

thank you so much!