Tuesday, November 18, 2008 - Block 4A

Handed back worksheets on distance, time, speed. 18 problems. Gave full credit for first 10 correct and half credit for more than 10. Max score in gradebook = 14 out of 10.

Handed back Act-A-Graph homework and quizzes

Asked if there were any questions.

Handed out fill in blank distance, time, speed worksheet to people who got less than 10 on the homework.

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.

Students did lab.

Didn't assign lab write-up

Lab write-up: Name, Partners, Date
Title - Ball Roll Off Table
Introduction: Explain in words how you measure the speed and how you keep the speed constant from run to run.
Data Table: Make a data table of all data and averages
Calculations: Show your calculation for time it takes the ball to fall. Show the equation, plug in values, show result with units.
Show your calculation for the horizontal distance the ball moves through the air. Show the equation, plug in values, show result with units.
Conclusion: Give the result (did you land within the circle, if not, what went wrong?