Final Exam Physics 151 block 6 2004 due at noon on Wednesday

As always, use the pre-owned paper supplied. Explain all your reasoning and show all your work. Do not consult anyone but me or your calculator. When you’ve finished, re-read your work, cross out whatever you no longer believe to be true, and make sure you have answered the questions.

1) (5 points) Suppose you drop two rubber balls, identical except that one has twice the diameter of the other. Which hits the ground first, and why? Sketch a piece of rubber that would hit the ground even sooner.

2) (20 points) The elephant and the fox are both four-legged mammals, but the elephant is much bigger. (Bet you didn’t know that.) Please discuss the repercussions of this size difference. Include a comparison of (a) skeletal structure, of (b) gait, of (c) speed, and of (d) the ratio of daily food intake to body weight (This part is worth more points.). To allow you to be quantitative, let’s assume that the elephant is ten times as tall, and long, as the fox.

3) (15 points) Suppose that in 1960 the biology department of the University of Southern North Dakota at Hoople carelessly released a crateful of Razorback Varmints, an Australian species particularly fond of winter wheat. By 1965 they were infesting wheat fields 5 miles away from the campus. Flatland Wheat Farms, located 15 miles away from Hoople, later had to change to soybeans when the varmint infestation reached them. In what year would you figure they had to make that change?

4) (10 points) The Mississippi, as do other rivers, spreads out into a delta as it nears the Gulf of Mexico. That is, it becomes very much wider, and splits into multiple channels. What are the consequences of this?

5) (15 points) You’re digging a 100-pound rock out of the ground. The rock is located 8 inches from the pivot of the shovel and your hands are located 3 feet from the pivot. With how much force must you push down on the handle? Make a nice drawing of this lever and of the lever that is your forearm (the one we considered on the last test). Please comment clearly and succinctly on the different advantages of these two different levers.

6) (15 points) Consider our bones. Extol the merits of their design, and explain why they’re not thicker or thinner than they are, why they’re not uniform (made of the same density of the same stuff) throughout, and why they’re cylinders (kind of hollow ones) and not some other shape.

7) (5 points) A really small air bubble under water tends to disappear, but a bigger one does not. Why is this?

8) (10 points) Sketch a front view of a fish. Indicate the center of buoyancy and the center of gravity, and explain why it is good that they are where they are.

9) (5 points) Suppose the wool on a 50-pound sheep weighs 2 pounds. How much should the wool on an 80-pound sheep weigh?

Here are a few (hand-written) equations. If you don’t see what you want, ask for it.