# Compare your prediction to reality

Now, your instructor will provide an example of a real cart and a real ramp. You will be given a spring. Your job:

Predict the distance L the cart -- attached to YOUR spring -- will travel down the ramp when it released from rest.

Your score for today will be computed in the following manner:

```
--------------------------------------------------

+/-  4 cm                        6 out of 6

+/-  7 cm                        5 out of 6

+/- 10 cm                        4 out of 6

any other                        3 out of 6
---------------------------------------------------
```

You may add to your score by showing careful, neat work in determining the spring constant and predicting the distance rolled.

Bonus!

If your prediction was NOT correct, can you explain the actual result by including friction in the calculations? You may regain the points lost in your prediction if you compute the coefficient of friction μ required to explain your measurements.