Lab Issues

(with many thanks to Dr. Suter for his work on his own page!)

General:

For specific labs, scroll down or go here for direct links.

Buckyball video:

Experiment 1: Where are We?

Annalemma.com: the connection between clock time, calendar, and "the sun’s position".

Also, check out this site for a good discussion of the reasons for the "corrections" we had to make to our calculations that depended on date.

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Experiment 2: Density

What should be written for conclusions to the lab work on Density? Look on page 3, of the assignment. Use the "Conclusions" section of the report to answer these questions.

Page 5, of the lab assignment asks for specific values for "Error" and "Relative Error". These can be answered only if we have an "accepted value" for the density for our granite pieces. The accepted value range according to the 63rd Edition of the Handbook of Chemistry and Physics is 2.64 – 2.76 g/cm³.

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Experiment 3: Uniform and accelerated motion

Check out the links on the lab reports guidelines page.

Experiment 6: Mechanical and Electrical Equivalent of Heat

Group results:

• Section 4
• Section 5

Remember to re-check your calculations, especially if you get numbers in the hundreds of joules per calorie!

A common mistake in the MEH section is to use the wrong mass. Think about it: the work being done is to lift a mass (in kilograms) against gravity; which mass is being lifted? The heat being generated goes into heating a mass (in grams); which mass is being heated?

In the EEH section, be careful to use the formulæ correctly:

• Electrical power = volts ´ amps
• Electrical energy = power ´ time in seconds

Section 4 Group Results
(1:00-2:30 Thursday)

Section 5 Group Results
(2:30-4:00 Thursday)

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Group presentations

The assignment for lab is to be ready, with your lab partner, to present to the members of your lab section the answer to one of the eight questions. This means an oral presentation in which you explain the basis for the answer. You will have a maximum of five minutes. Your presentation will be graded on a 10-point scale. The average score given by your lab mates will be 30% of your score; the other 70% will be given by the instructor, for a total of 20 possible points. This will be your lab grade for this session (no written report is necessary).

The question you will actually answer will be determined by a random draw during class on April 11; those with high numbers get to pick first. If you are not present, you will be assigned a question by the professor from those not chosen.

1. Why are high-mass stars shorter-lived than low-mass stars? (Exercise 13, p. 723)

2. Answer the following. (Exercise 9, page 745)
   1. Suppose the parallel mirrors of a light clock are 150,000 km apart. In the clock's frame of reference, how much time is required for a pulse of light to make a round trip between the mirrors? b) Would your answer to this question be different if your measurements were made from a frame of reference that moves relative to the light clock? Explain.

3. Some stars contain fewer "metals" (elements other than hydrogen and helium) than our sun does. What does this indicate about the age of such stars relative to the age of our sun? (Exercise 16, page 723)

4. Muons are elementary particles that are formed by the interaction of cosmic rays with gases in the upper atmosphere. Muons are radioactive and have average lifetimes of about two millionths of a second. Even though they travel at almost the speed of light, muons are formed at such extreme altitude that very few should be detected at sea level - at least according to classical physics. Laboratory measurements, however, show that most muons do reach the Earth's surface. What is the explanation? (Exercise 21, page 746)

5. Why does an observer at a given location see one set of constellations in the winter and a different set of constellations in the summer? (Review Question 2, p. 722) During a total solar eclipse, stars can be seen in the sky. Which constellations would an observer see during an eclipse during the summer? During the winter?

6. We see the constellations as distinct groups of stars. Discuss why they would look entirely different from some other location in the universe, distant from Earth. (Exercise 9, page 723)

7. In his novel From the Earth to the Moon, Jules Verne stated that occupants in a spaceship would shift their orientation from up to down when the ship crossed the point where the Moon's gravitational pull became greater than the Earth's. Is this correct? Defend your answer. (Exercise 26, page 746)

8. A black hole is no more massive than the star from which it formed. Why, then, is gravitation so intense near a black hole? (Exercise 22, p. 723)

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