Friday, November 21, 2008 - Block 4B

I was at the NSTA convention so had sub Julie Burich.

Notes for sub

Students will be doing the Ball and Ramp Lab to investigate acceleration. Ramps are on the back bench. I have put 8 pink stopwatches and 8 steel balls in a bin by the ramps. Please make sure all equipment gets put back.

Go over content objectives on flip chart.
Students will be able to describe the motion of a ball rolling down a ramp in both words and using a graph and be able to interpret the graph.

Before students do the lab, describe the lab in detail, showing the setup and how to make the measurements. For the first measurement, place the ball 10 cm from the end of the ramp. Release it and time how long it takes to go down the ramp. Show them how to hold the ball in place with a ruler and then release it by lifting the ruler straight up. Please tell the students not to put tape on the track (sides are ok) and not to mark on the track (they can mark on tape that they put on the sides of the track.) Make sure the students measure the distances in centimeters and not inches. Show where the equipment is and tell students to put the equipment back when they are done. I usually go around and collected stopwatches and steel balls when students were done with the measurements.

Pre-lab: Sketch distance vs time axes on the board. Tell them that the first point on their graph is (0,0). If the ball is already at the end, zero distance away, it takes zero time to get there. They MUST include this point in their graphs. Ask the students to sketch in their notes their prediction of the shape of the graph with a brief explanation of why. You might wander around and check what they draw or you might have some students show their sketches on the board and explain why.

I have supplied an overhead with the lab groups. The groups are either 3 or 4.

Please have students do the lab on the floor. If you are brave, you can allow a couple of groups to set up in the hallway outside (NOT groups 1 or 2). If they need books, they can use the yellow textbooks in the back of the class. Just please make sure they get put back in order. I suggest two books.

Lab handouts are by the ramps. Students will work in groups of 3 or 4 to do the lab. Every student will hand in their own report by the end of the period including the graph. Graph paper is located at the front of the class.

Students will be using the ramps on the back bench. Please ask the students to handle them with care since they are easily dented and damaged.
Please make sure you have all 8 pink stopwatches and all 8 steel balls at the end of class. Sometimes things go missing in this class. Do NOT let the students wander around the class messing with anything not directly associated with their lab.

Lab wrap-up. Revisit content objectives.
How well did your predictions agree with experimental results?
Describe the motion of a ball rolling down a ramp in words (speed increases) and how this looks on a graph (starts with shallow slope and then gets steeper as the speed increases).
How would the graph change if you used no books and just placed the ball on a level ramp?
How would the graph change if you used twice as many books making the ramp steeper?
What would happen if the ramp were vertical?

This lab should not take the entire period but I leave that up to you. (Since it is Friday afternoon, just the lab itself might be enough). Some students will struggle making the graph. It works out well if you hold the paper vertically and go up by 25 in major units. If you need the entire period, fine, if all students finish early and you need an additional activity, there is an additional exercise worksheet on distance, speed, and time. Students can start this and if they don’t finish, complete as homework. If you use this, please emphasize that students need to do the work on a separate piece of paper (no room on the sheet) and that they need to show all the steps of the problems solving strategy they learned in class (see fill in blank worksheet that they have already done). I will leave these worksheets on my desk.

You can leave anything you collect from this class in the wire bin.

Please make sure the students put up their stools on the benches at the end of class. Do not let them crowd near the door or skip out early.