PHYS140 FAQ

How does changing gears make a bicycle easier or harder to ride?

Fri, 03 Feb 2006 14:00:05 -0600

Q. Changing gears on a bicycle makes it easier or harder to pedal. Changing the front gears to bigger gears will make the bicycle harder to ride, while changing the back gears to bigger gears makes it easier to ride. Why are they different?

Drinking Brid

Tue, 01 Nov 2005 14:16:22 -0600

Q. There are many many explanation of the drinking bird on the web - just google "Drinking Bird" and you'll find more information than you could ever want! Here I'll write only a brief description of what causes the bird to drink.

Lamp and spinning fan

Tue, 25 Oct 2005 15:52:23 -0600

Q. In DR we saw a little fan in a glass bulb. When we turned on a light shining on the fan it began to spin. Why?

Heated metal plate

Wed, 19 Oct 2005 23:42:27 -0600

Q. What happens to a metal plate when it's heated? What about if the plate has a hole in the center?

Gears sizes and force

Wed, 12 Oct 2005 00:22:31 -0600

Q. If you want to minimize the force you exert on the pedals what sizes gears should you have at the crank sprocket (at the petals) and the freewheel sprocket (at the wheel)?

Bike gears and work

Mon, 10 Oct 2005 13:10:26 -0600

Q. How do the concepts of work and energy relate to the gears on a bicycle?

The spring constant

Mon, 03 Oct 2005 23:29:34 -0600

Q. What is the spring constant? How do you calculate it? Does it change if we use a different mass to calculate it?

Blocks and balls

Mon, 19 Sep 2005 11:07:11 -0600

Q. In lecture and in DR, we saw two balls crash into two wooden blocks. One ball was like a superball and the other was made out of clay. The block that the superball hit fell over, while the block that the clay ball hit did not. I don't get it -- what happened?

Spinning Wheel and Rotating Stool

Sat, 17 Sep 2005 13:37:00 -0600

Q: In DR I sat on a stool and held the spinning bicycle wheel. When I flipped over the wheel I started to spin. What was going on??

Two falling balls of different masses

Sat, 17 Sep 2005 13:18:04 -0600

Q: In DR we dropped 2 balls of different masses from the same height and saw that they hit the floor at the same time. This is confusing to me - shouldn't the lighter ball hit first since it has less inertia and the same gravity as the heavier ball?