Dot Physics

Archives for April, 2010

My two favorite curricula

Today is show and tell. I would like to show and tell you about two of my favorite textbooks for physics. Yes, I know. I have talked about these before, but you can’t stop me. Both of these are alpha-super-awesome. Matter and Interactions This is a Calculus-based introductory physics textbook (from Wiley). The intended audience…

Airlock examples

I was going through and tagging some old posts. While looking at a post attacking the movie Sunshine, I accidentally found something else on youtube. Gravity in Sunshine I could not find a clip online of the scene I want, so I made a cartoon. Basically, (oh – spoiler alert) some guys are trying to…

Basics: The electric field

Suppose I take a 1 kg ball and hold it near the surface of the Earth. What would be the gravitational force the Earth exerts on this ball? And I could say “g” is: The magnitude of this force would then be 9.8 Newtons. And, if I replaced the ball with a 10 kg ball,…

Why is it dark inside?

This was a great question. When you come inside after playing in the sunny outside, why is it so dark? Simple answer: because your eyes are smart. When you are outside, there is a lot of light. Really, it is too much light. To compensate for this, your pupils (the part of your eye that…

I don’t know. One the one hand, it would seem that teachers (and really I am talking about grade school level and maybe middle school) need to be good an managing students. What should a teacher have to help students? I think the first big question is “what is going to happen in the classroom?”…

So, I complained about MythBuster’s explanation of relative velocity. How would I explain this? I would start by saying that velocity is relative. Here is the definition for velocity: I put the “avg” in there because it is more true. If the acceleration is zero, I could drop this. For the rest of this post,…

Textbook Update

I have made some small changes to my physics textbook. Basically, I have been updating all my old posts so that you can find stuff. What I did was include tags for each topic. For instance, suppose you are looking at projectile motion. Well, I include a link to examples with projectile motion. Some of…

MythBusters and physics terms

In the last episode of MythBusters, they tried to reproduce the following experiment. Suppose you are driving in a car at 60 mph and you shoot a ball backwards at 60 mph (with respect to the car). Will the ball just drop (with respect to the ground)? Actually, it is a cool demo – I…

Greater is Greater

I gave the following question on my last physical science (physical science for non-science majors) test: Block A has a mass of 10 kg and volume of 100 cm3. Block B has a mass of 1 kg and a volume of 1 cm3. Which block has the greater density? Which block has the greater volume?…

Surface Tension vs. Floating

Check out this video demo: So, that is just plain water. If I am careful, I can make that thin aluminum disk stay on the surface of the water. This is not the same as floating in Archimedes principle. It is different. This is staying on the surface because of surface tension. Bouyancy I think…