# Slope amplitude help

1. Dec 9, 2007

### boberth2o

Ok as I am a Newb at pyshics I need some help with my homework. *sigh* This is going to be a couple of de de de questions. And here we go:

1. What does the slope indicate on a period(time) vs. amplitude(degrees) graph?
2. What does the slope indicate on a period(time) vs. length(cm) graph?
3. What does the slope indicate on a period(time) vs. mass(g) graph?

2. Dec 9, 2007

### Kurdt

Staff Emeritus
Welcome to the physics forums boberth2o! We do not provide full homework solutions here as the student will learn nothing. The student must show some effort at solving the questions.

What do you think the gradient of each graph indicates? Think of how you determine the gradient or slope.

P.S you posted in the wrong forum, there are homework forums located here:

https://www.physicsforums.com/forumdisplay.php?f=152

3. Dec 9, 2007

### boberth2o

Thanks, I searched througth the main forum searching for somthing like this but I must of missed it.

Well im not fishing for answers, heres what im doing, I am writing a report in the 'formal laboratory report' format. Under analysis I have to determine what the slope indicates. At this point I cant seem to come up with the answer. I know to determine the slope, its the portion under the graph (correct?). If you could goad me into the right direction I might be able to find it myself.

4. Dec 9, 2007

### Kurdt

Staff Emeritus
The gradient or slope of the graph tells you the rate of change of the graph at a particular point. When you first come across it at school it will be finding the slope of straight line graphs, where you measure the change in y and change in x and divide them. In other words:

$$gradient = \frac{\Delta y}{\Delta x}$$

So for your graphs what physical quantity would you arrive at if you divided the y axis by the x axis.

5. Dec 9, 2007

### boberth2o

That would make it period/amplitude, how do I represent that? T/(degree sign)

6. Dec 9, 2007

### Kurdt

Staff Emeritus
I think you may have plotted your graphs wrongly. Normally time goes along the x-axis. an angle divided by time will be an angular speed, radians per second.

7. Dec 9, 2007

### boberth2o

Yes but amplitude it the manipulated variable, I was sure that the manipulated goes on the x axis (max roy)

8. Dec 9, 2007

### Kurdt

Staff Emeritus
OK this looks like an SHM lab. Apologies I didn't pick up on that earlier. What exactly is the purpose of the lab may I inquire? I presume you are investigating period and have you been told to plot those graphs?

9. Dec 9, 2007

### boberth2o

We are making a lab on the pendulums swing, how the mass, length, and amplitude affect the swing.
The Pendulum is set a 10 degrees and dropped, once the pendulum reaches zero degrees or perfectly up and down, we time how long it takes to get ten full swings in. Then manipulating the parameters we do it again and again. Now using the average of the data (three trails for each variable) we graph the results.

10. Dec 9, 2007

### Kurdt

Staff Emeritus
I wonder if you've ever derived the period of a pendulum before? For a simple pendulum a lot of things cancel out and one obtains the familiar equation:

$$T = 2\pi\sqrt{\frac{l}{g}}$$

Hidden among that in the assumptions and the derivation are the quantities you're dealing with, namely mass and amplitude expressed as angle and the mass of the pendulum. I will say that to gain anything useful out of the graphs you may have to do them again. You will notice that the equation gave above for period isn't directly proportional to the length.

I'll be offline after this since its quite late where I am, but I'll direct some other homework helpers here.

11. Dec 9, 2007

### boberth2o

Thank you but all I need to figure out is the word(s) that describe the period/amplitude. like the example displacemnet on a time velocity graph.

12. Dec 9, 2007

### robphy

instead of amplitude, do you mean PHASE?

13. Dec 9, 2007

### boberth2o

No I was told to use amplitude.

14. Dec 10, 2007

### Kurdt

Staff Emeritus
Ok, for graphs 1 and 3 you should get a horizontal straight line graph. The slope of this is 0 and this indicates that period has no dependence on amplitude or mass. For period length, you should get a curve which indicates a non linear dependence, and if you plot period squared against length you will get a straight line graph, the slope of which will be:

$$\frac{4\pi^2}{g}$$

I suppose my confusion arose from the fact that normally one plots a period squared length graph.

15. Dec 10, 2007

### boberth2o

Well the funny thing is that I handed in that report today and then took note on this very stuff, mostly SHM.