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Physics 109n Homework #4

Due Tuesday October 1, 1996

Important! Question #1 must be done on Thursday 26 September!

1.The moon will go into eclipse beginning around 8.45 p.m. Thursday night.

(a)Draw three sketches of its shape as the earth's shadow covers it-these sketches should all have the moon partially in shadow.

(b)Estimate from your sketches the relative size of the moon and the earth's shadow the moon is passing through.

c)Is the moon's path through the shadow such that the middle of the moon passes through the middle of the shadow, or is it a bit to one side?

(d)Is the moon still visible to you when it's completely in the shadow? If so, where is the light coming from?

(Note: if it's cloudy Thursday night, this question is cancelled).

2. (a) How did Galileo get tenure?

(b)How did he get an even better job?

c)How did he get crossed up with the Jesuits?

(d)How did he alienate Pope Urban VIII?

3. In an experiment on scaling carried out in 1883, a dog of mass 3 kg. and surface area 2500 sq. cm. was found to need 300 calories a day to stay alive and warm (no exercise or weight change). Another dog of mass 30 kg. and surface area 10,000 sq. cm. was found to need 1100 calories a day.

(a) Do the calorie requirements correlate better with mass or surface area? Explain what you would expect. How precise would you expect the correlation to be?

(b) Make an estimate of your own mass and surface area, and, assuming you are doglike for purposes of this question, how many calories do you need a day to stay alive, without exercise and at constant weight?