# Homework Help: Finding hight of an inclined palne with its lengh and a force

1. Jan 30, 2009

### RockenNS42

I had several inclined planes, all with the same height(15.5cm) I then pulled up a trolley (600g) with a force metre here are my results
length force
66.8 1.5
57.1 2
47.6 2.5
38.3 3
29.4 4
21.6 5.5
16.3 6.5

I now need to manipulate the raw data to find the height (which is already known to be 15.5)

2. Relevant equations

work done= energy transferred
?fd=mgh?

3. The attempt at a solution

I was trying
fd=mgh

for example for the first one
1.5 * .668 = .6kg* 9.8 *h
17cm

I'd really appreciate some help, thanks

2. Jan 30, 2009

### Delphi51

Your calc looks good! You could repeat it for each set of data and then take an average to get an estimate of the height.

The trouble with an average is that the experiment may have some consistent errors that get included. You have a better chance of getting an accurate result if you analyze experimental data on a graph. Can you think of a way to make your Fd = mgh look like the y = mx + b of a straight line equation? Clearly the b is zero, so compare
Fd = mgh with y = mx.
The F and d are your measurements sort of corresponding to y and x, so you want to get one of them on the right side. You could use
F = mgh/d
Comparing that with y = mx, knowing you want the slope to be the h, you see that you should plot F on the side and mg/d on the bottom. Graph the data that way and find the slope. If you get a y-intercept other than the zero theory predicts, you can be happy knowing that you are eliminating some of that consistent error!

3. Jan 31, 2009

### RockenNS42

I tried that and it works good.
Thanks alot, I never really thought of doing
it that way (F=mgh/d) And the slope turned out
to be colse to the orginal height. :)