Monday, Nov 17, 2008

Collect Act-A-Graph Homework

Asked it there were any questions on Act-A-Graph Lab
Quiz on Act-A-Graph

Show problem solving strategy for distance,time,speed problems
Did an example using the problem solving strategy.
Handed out revised worksheet on distance, time, speed problems with fill in the blanks to force the students to use the problem solving strategy. Went over first problem explaining how to fill in the blanks. Gave the students until 2:20 to work on it, giving help when students had difficulties.

Handed out rulers and two pennies per group. Explained set up for projectile motion lab. Most students determined that the two pennies hit the ground at the same time.

Showed diagram on board of ball rolling off a table. As it approached the edge of the table, I showed positions of the ball equal distances apart. This indicates constant speed. Since the ball rolling off falls at the same rate as a ball dropped from the same height, I showed pictures of the two balls falling the same vertical distance in the same times. It turns out that it takes a time t = sqrt( 2 * h/10) for a ball to fall a vertical distance h when dropped. This is the same amount of time it would take even if it had some horizontal speed.

Showed lab set-up with track, launcher and ball. If you launch the ball the same way each time, you should have the same constant speed. Measure a distance of track with a meter stick. Put tape at the the start and end points. Use a stopwatch to measure the time. This will give you the speed.

Multiply this speed by the time in air and you get the horizontal distance the ball travels from the table. The goal is to have it land with a circle of the inside diameter of a roll of tape. You get one try.

After that, use a motion detector to measure the speed. Compare with the value you got using the meter stick and stopwatch.

There will be a lab write-up. Go over that next time.