3-15

One Friday the thirteenth, I walked into class and picked up papers 11 and 12 on Mr. Manning’s desk. The first thing we did was tackle the two daily questions. The first read:

Anna Litical is practicing a centripetal force demonstration at home. She fills a bucket with water, ties it to a strong rope, and spins it in a circle. Anna spins the bucket when it’s half-full of water and when it’s a quarter-full. In which case is more friction required to spin the bucket in a circle?

The equation needed is F=mv2/r. The answer is half-full because doubling mass also doubles force needed.

The second question was: The Cajun Cliffhanger at Great America is a ride in which occupants line the perimeter of a cylinder and spin in a circle at a high rate of turning. When the cylinder spins very rapidly, the floor is removed from under the riders’ feet. What affect does a doubling in speed have upon the centripetal force?

There is four times the force because of the relationship between force and velocity. F~v2.

Then there was an argument over the use of “affect” in the second question.

Next, we took a look at page 2, question 2. We learned that the direction of acceleration is towards the middle because force and acceleration ALWAYS, ALWAYS have to be in the same direction.

We also went over the notes found on page 9 and watched a clip from Rocket Man. The homework was pages 11-13.