Student Designed Force Lab

Here is the design handout: IA-Des-Description.docx

For this lab you are going to design an investigation, gather good data, and make a graph of it. You do not need to calculate anything, just graph the data. If it looks like it is linear, you can put a straight line through it and show the slope, but that is optional.

You may turn this lab in with a (1) partner, or do it individually, but you may gather data in a group of 4 if you wish.

Here's the instructions I gave in class before the lab:

•Intro of Force Lab

8:59IBI 04-06-02 The Force Lab Introduced

Here is how I graded the lab:

3:47HTPIB04 Force Lab Grading

For this Lab, you need to turn in:

• Your design of the lab, (See below - this is most of the lab)

• A Data Table with units and uncertainties (High -Low)/2 of your trials

• An appropriate graph (You should use an X-Y scatter graph) of your data either computer generated, or on graph paper. If you know how to add error bars, you can do that, but at this point it is optional. If it looks linear, you can put a line through it, but again this is optional.

(Des) Design:

Aspect 1: Stating the problem and listing the variables

• State the problem concisely, and

• list the independent, dependent and controlled variables.

Independent variables are the ones you manipulate, dependent are the variables you measure, and controls are the things that stay constant.

Aspect 2: Method for control of variables

• How you will manipulate the independent variable,

• measure the dependent, and

• make sure that the controlled variables don’t change.

• Draw a diagram, include measurements of anything that matters,

tell what equipment and materials you used, and give a step by step description of what you did.

Aspect 3: Method for collecting sufficient data

• You need to do a sufficient number of variations (5-10) of the independent variables,

• do an adequate number of trials (3-5) of each variation, and the variations should be if possible well distributed throughout the possible range of variations. If you are going to use this lab as your OIT lab you should do at least 10 variations, and 5 trials of each variation.

• You need to talk about what trials and variations you did, and why you chose these variations and number of trials. State them explicitly.

(Variations are like 5^o, 10^o, 15^o, 20^o, 25^o, etc, and trials are repetitions of the same thing)

Example:

Suppose I am doing an experiment to see how the parallel force depends on the angle of an incline.

Aspect 1: (After a bit of introductory information)

The purpose of this investigation, then, is to determine the relationship between the force necessary to keep a wheeled cart from rolling down an incline, and the degree of that incline. The independent variable is the degree of incline, the angle it makes with the horizontal, the dependent variable is the force needed parallel to the plane to hold the cart stationary on the plane, and the controlled variables include, but are not limited to the mass of the cart, the position on the plane, the type of surface used, and the angle of the force scale used to measure the force.

Aspect 2

Our setup consists of a 2.0 m long inclined plane that we propped up using a pile of books. (Insert a labeled diagram here) We kept the mass of the cart constant at 1.85 kg, and always positioned the cart in the middle of the plane. The angle we measured using a protractor placed on the table surface, and we measured the force using a 20 N force scale for all trials. We took special care to keep the force scale parallel to the surface when we measured the force. To gather a data point, our procedure was this: First, we propped up the plane to the angle we desired, and measured this carefully keeping the protractor level with the table surface. Second, we tipped the force scale parallel to the plane, and made sure the scale read zero. If not, we adjusted the zero. Then we carefully attached the cart in the middle of the plane, and very slowly let it exert a force on the scale. We then read the force on the scale.

Aspect 3

We chose to try the following angles: 10, 20, 30, 40, 50, 60, and 70. We could not get the plane to remain stationary for 80 degrees or higher. Because there was a fair amount of trial to trial error, we did five trials of each angle to make sure that the measurements were repeatable.