Today all that we accomplished was to gather data for the frictional force experiment. Here is a picture of our basic setup:
This was one of the two different sets of surfaces… it was to simulate a car tire on concrete. I asked our autos teacher to attach some real tires pieces on a block, but the size was a bit prohibitive. The other was he classic wood on wood. Tomorrow we whiteboard the results.
We shared our values for the acceleration of an object in free fall, then worked a sample problem. I used the ‘ol catch a dollar bill and you keep it’ problem to introduce the problem. Challenge a student to catch a dollar bill as it slips through his/her fingers. The elbow and wrist stay on a table and Georges head gets lined up with the fingers. The discussion naturally comes around to that the student can’t react fast enough…. so how fast would you need to react to catch it? Do a free fall problem and find out…. about 122 ms (~7.4 cm from the edge of the dollar to George). If there is enough time, the students can catch a falling ruler and calculate their own reaction time.