PHY 133 Lab Manual

PHY 133 Lab Manual Revised December 2013’

Links to this course’s lab experiments are below. There are hard copies in the laboratory for you to follow as you do the labs; you don’t need to print them unless you want copies for some other reason.

At the end of each lab is an answer sheet. You will be given a copy of this to fill out as you do the experiment. Work in pencil so you can erase mistakes. The report you hand in for each experiment is to consist of (1) the completed answer sheet, and (2) a discussion of the experiment, as described below.

lab\1.pdf

For each lab, write a report that would clearly explain the experiment to someone had not done it, but has a knowledge of physics. I will be particularly looking for you to explain how the apparatus works. (I want to be sure you understand that.) The discussion should have the following format:

1) Objective (What you were trying to do.)

2) Apparatus and Procedure (How you did it.)

3) Conclusion (Whether it turned out as expected.)

The discussion need not repeat what your reader could see by turning the page to your answer sheet. Try to avoid minute detail which distracts from your main points. (You are explaining the basic idea of the experiment, not providing step-by-step instructions.) Just explain what was going on, and tie together the other pages you have attached. Don’t be afraid to make sketches of the apparatus; they are often easier for you and clearer for your reader than words.

Good Example:

Report on Experiment 1C: Acceleration due to Gravity

(Your Name)

The purpose of this experiment was to verify that a freely falling object accelerates at 9.8 m/s².

One of us dropped a golf ball from near the ceiling. As it fell, its position was periodically recorded by a motion sensor that was on the floor. This sensor works by sending out pulses of sound and timing how long it takes the echoes to return. The sensor was connected to a computer which calculated velocities from the position data, and plotted a graph of velocity versus time. The acceleration is this graph’s slope. The result agrees with the accepted value within our level of uncertainty.

Bad Example:

Report on Experiment 1C: Acceleration due to Gravity

(Your Name)

We turned on the computer and interface. We then opened Science Workshop on the computer, and dragged the digital plug icon to channel 1 on the picture of the interface. On the list that appears, we double clicked on motion sensor. The motion sensor was placed on the floor, aimed upward, somewhat to the side of where the ball would land. We then clicked on Record. When the writing got faint, we released the ball, then clicked stop when the ball hit the floor. We then dragged the graph icon to channel 1. … (Imagine about two more pages of that.)

(Not only does that take longer to write, but it's very easy, in all of that, to never actually get to the point. Don’t bore or confuse your reader with a vast amount of trivial detail, even though that might be what took most of your time and attention.)

Bad Example:

The purpose was to verify that a freely falling object accelerates at 9.8 m/s². We took the apparatus and made the measurements described in the instructions. The measured and calculated values did agree with other.

(Your report should stand on its own. Your reader could not possibly picture the experiment based on just what you wrote.)

Some people like to write the discussion ahead of time so they can get out of the lab sooner. Others feel they can explain the experiment better after they've done it. That’s your choice. Also:

- Don’t simply copy what your partner wrote or what the instructions say. Similarly, do not copy calculations. Everyone should do the calculations so that everyone understands how, and so you can check each other for mistakes. If everyone in your group has the same arithmetic error, or wrote identical discussions, expect verbal abuse from the instructor.

- A maximum of four students is allowed in each lab group. Except for a few experiments where it's necessary, if your paper is one of more than four with the same data, I'll send you back to do it over. (If yours isn't working, don't use your neighbor's data.)

Review of Uncertainties:

- When adding or subtracting numbers, add the uncertainties:

Example: (4.3 + .2 cm) - (2.7 + .2 cm) = 1.6 + .4 cm

- When multiplying or dividing, add the percent uncertainties:

Example: (4.3 + .2 cm)(2.7 + .2 cm)

= (4.3 + 4.65%)(2.7 + 7.41%)

= 11.6 + 12.06%

= 11.6 + 1.4 cm²

To find what percent .2 is of 4.3: .2/4.3 = .0465 = 4.65%

To find what 12.06 % of 11.6 is: (.1206)(11.6) = 1.4

PHYSICS LABORATORY SAFETY GUIDELINES

Genesee Community College

Although the most dangerous thing you will do for this course is ride in a car to get here, there are hazards involved with working in the physics lab. These will be pointed out as they come up, in the written instructions for each experiment.

It is the student’s responsibility to:

1. Read the current exercise before coming into the laboratory to be aware of any cautions or warnings. This also helps avoid confusion and wasting time during the lab period. It is your responsibility to be aware of these warnings, to understand them and to take them seriously. Ask the instructor for clarification if necessary.

2. Pay attention to and understand any additional instructions the instructor may give verbally while the experiment is in progress.

3. Inform the instructor if you have a medical condition that could affect your ability to perform laboratory exercises. Reasonable accommodations will be provided.

4. Notify your instructor of any broken glassware so he/she can dispose of it properly. Do not pick up broken glass with your hands. Do not throw broken glass into the wastebaskets.

5. Report all injuries to your instructor regardless of how trivial they may seem.

6. Ask, if it is unclear what you should do. On rare occasions, a student may find a novel way of causing injury that was not anticipated in the directions. Have the instructor help you to not be that student.