Interesting Physics Stuff
Physics 126 Spring 2011

This page is under construction

On this page, we have tried to gather some "interesting physics stuff" as relates to this course. If you have any comments, suggestions, or things that you think would be interesting, let us know!

Questions: Background Stuff
Questions: Kinematics

Demos: How knowing physics can save your life
Demos: Using physics to model people
Demos: Traveling around a rotating black hole

Questions: Background Stuff

Question: Does physics use the "metric system?"
Answer: There are two answers to this

Physics doesn't require any specific system of units. When you push on something, it moves -- that is physics. The units you choose are up to you. But
The term "metric system" really isn't correct. In this course, we use the System International (SI). Why? Well, the "metric system" really isn't metric. The length (meter), and mass (gram) are both metric, but seconds are not a metric unit. This is because the next larger unit (the minute) is not a power of ten larger. Actually the time system is a sexigesimal (60) system. You can thank the Sumarians, who thought that the number 60 was cool because you could evenly divide it by so many integers (2,3,4,5,6,10,12,15,20,30). It also didn't hurt that the sun takes approximately 360 (60x6) days to move around the sky (that is also why a circle is defined to have 360 degrees -- the position at which the sun rises moves by about 1 degree per day).

Question: How do we know that physics is "correct?
Answer: We don't. All we can say is that the physics we know has been able to explain all of the tests (observations of the world) that we have thrown at it. If a new observation comes along, then the physics will have to be modified.

Questions: Kinematics

Question: Is it possible for Tracy Mac to really "hang in the air?"
Answer: Well, it depends upon what you mean. Since he is always under the acceleration of gravity, his speed is a line of constant slope. At the top, his speed is zero. However, compare the amount of time he spends in the top 15cm of his jump to the bottom 15cm of his jump (assume he can jump 76cm.)

Question: Although the maximum range of a projectile in vacuum occurs for a launch angle of 45 degrees above the horizontal, many "long range" military guns fire at greater than 45 degrees to get longer range. Why? [Hint: consider the fact that the air density decreases with altitude.]
Answer: Since the air is less dense at greater altitude, there is less air resistance, so the projectiles can fire futher.

Demos: How knowing physics can save your life

What happens when engineers do not properly account for all of the physics they learned as a freshman:
The Tacoma Narrows Bridge

Demos: Using physics to model people

Here is an example of a detailed physics model of a person. The idea is that to make better prostheses, researchers need to understand how the joints work. So this example is a test that a group of researchers made to test their model.
Adonis jumping.

Demos: Traveling around a rotating black hole

This is a bit esoteric, but somewhat neat too.
Rotating Black Hole.

If you have any questions, or comments, please e-mail them to me at doty@denison.edu. Thanks!