Looking Back at Semester One

Photo by Andrew Mccluskey used with Crative Commons license

Now that we've finished the first semester, I'd like to take a minute to look back and reflect. Often, teachers ask about what topics were the most interesting or fun to study, but I'd like to take a slightly different approach here.

What topic or topics from semester one did you find the most frustrating? Be clear in why you're choosing what you're choosing... ... was it frustrating because it was difficult? Not well explained? Boring? Something else? I'm curious to see if we notice any recurring ideas. Please post in the comments section!

Projectile Motion

This really cool simulation is courtesy of the PhET project at the University of Colorado. Play around with it until you get comfortable and familiar with the controls.

Answer these questions as comments. Don't answer identically to what someone else has already said--either add to his or her response, indicate that you disagree with the response, or answer a question that hasn't been already answered. Please only comment on 2 questions so everyone has a chance to get some points.

1. What is the range of a golf ball if it is launched at a 40° angle with a speed of 15 m/s?
2. What is the total time the golf ball from question (1) is in flight?
3. Neglecting air resistance, how does the launch speed affect the projectiles overall range?
4. Neglecting air resistance, how does the launch angle affect the projectiles overall range?
5. Neglecting air resistance, how does the projectile's mass affect the projectiles overall range?
6. Of the preset choices, which 3 objects appear to be most affected by air resistance? How do you know this?
7. Neglecting air resistance, what launch angle produces the maximum range for a projectile?
8. Taking air resistance into account, what launch angle produces the maximum range for a pumpkin launched at a speed of 10 m/s?

Friction: Friend or Foe?

By Penubag (Own work) [Public domain], via Wikimedia Commons

We've been learning about forces this semester. Often, we treat surfaces as "frictionless" to simplify calculations. When we talk about machines, we sometimes "neglect friction" and assume the machines are ideal. By doing these things, it's easy to associate friction with something bad. It is true that there are many situations where friction is not desired, and engineers usually take steps to reduce friction in their designs.

However, that's not the whole story. Sometimes friction in desired. What examples or applications can you think of where friction is "the good guy"? Post your ideas in the comments section.

Photo from Mars

An amazing self-portrait has just been taken on Mars. Here are a few questions to get us started this marking period:

1. What is this a picture of?
2. What is the purpose of this vehicle's mission?
3. What do you hope or think scientists will learn as a result?

News from Space!

Artist's rendition of the newly-discovered planet orbiting nearby Alpha Centauri. (Photo used with permission from ESO/L. Calçada/Nick Risinger.)

This week, there are several popular news stories involving space. First, there was Felix Baumgartner's daring skydive from the edge of space. Then, on Wednesday, thousands of Californians witnessed a very bright meteor (thought to be a remnant of Halley's Comet). Finally, astronomers announced the discovery of an Earth-sized planet orbiting the Sun's next door neighbor, Alpha Centauri.

This has been an interesting week in astronomy! Answer some or all of the questions in the comments section.

1. Which of these news stories is most exciting to you? Why do you feel that way?
2. Does Baumgartner's jump make him the fastest human to ever travel through the air without being enclosed in a vehicle? Explain.
3. Halley's Comet orbits the Sun once every 76 years. How often does the earth travel through the remnants of Halley's Comet?
4. Alpha Centauri is quite different from the Sun because it is a binary system--there are actually two (or three if Proxima Centauri is included) stars gravitationally bound to each other. How would these two stars appear from the surface of the newly-discovered planet? Would they look like twin suns?