terminology of the calibrt program

Terminiology, Graphs, Question(s) about the Calibrt Program

Data and Graph by Student (also comments relevant to Exp 15)

Data and Graph by Student (also comments relevant to Exp 15):

The data below were taken by a student.

rb length (cm)	rb stretch (cm)	force (N)
9.7	0.9	0.67
10	1.2	0.94
10.5	1.7	1.3
11	2.2	1.5
11.5	2.7	1.6
12	3.2	1.8

The force vs. stretch graph is shown below:

The attached Excel file Exp 10 depicts the graph (exp 10 version5 for Version 5, which should work on older versions of Excel). I've added a trendline to show the deviation from linearity.

The next table depicts the calculation of force * distance products and totals. This will be relevant in Experiment 15.

rb length (cm)	rb stretch (cm)	force (N)	ave force (N)	dist on interval (cm)	ave force * dist (N cm)	total f * `ds (N cm)
8.8	0	0
9.7	0.9	0.67	0.335	0.9	0.3015	0.3015
10	1.2	0.94	0.805	0.3	0.2415	0.543
10.5	1.7	1.3	1.12	0.5	0.56	1.103
11	2.2	1.5	1.4	0.5	0.7	1.803
11.5	2.7	1.6	1.55	0.5	0.775	2.578
12	3.2	1.8	1.7	0.5	0.85	3.428

These calculations are easy to set up in Excel if you know how to use the Fill Handle

Quick reminder:

Set up the first row of calculations as on the worksheet. Highlight cells D - G in the row.

Move the mouse toward the lower right-hand corner of the highlighted area until the heavy + sign appears, then drag straight down to fill the desired columns).

If you don't know how to use the Fill Handle, then you might have to key in the calculations one at a time. However the amount data isn't that great and it woun't take too long to do so.

(On Experiment 15 you might find that you need to use the heavy rubber bands, or you might find that a few of the medium rubber bands work fine. If you use the medium rubber bands, your second set of data should give you the information you need.)

Question (terminology):

What is the difference between pendulum length, pendulum position, pendulum displacement, rubber band length and rubber band stretch?

Answer:

As used in the experiment, these terms have the following meanings:

Pendulum length is the distance from the ceiling or wherever the pendulum is supported to the center of the pendulum bob.
Pendulum position is the position of the center of the pendulum bob.
Pendulum displacement is the distance from the equilibrium position to the pendulum position.
Rubber band length is how long the rubber band is, from one end to the other.
Rubber band stretch is the difference between the length of the stretched rubber band and the length of the rubber band just before starts to stretch.

Question (CALIBRT):

When doing the calibrate program I get confused on what information to put in when it asks for instrument reading and measured quantity. And then it asks to multiply by a constant factor. Could you please help me figure this out?

Answer:

For example on the rubber band calibration:

The instrument reading is the length of the rubber band (read on the ruler, which is the measuring instrument).
The measured quantity is the force, as calculated from the mass suspended from the rubber band, or from the displacement of the pendulum.
The zero-point reading will be the length of the rubber band just before it begins to stretch.