In an effort to boost learning center enrollment for next semester, I held a free preview day this week. Four student visitors stopped by to check out the class. I hope they'll join us for the whole semester in the Spring!
We continued our study of simple machines this week and also used this knowledge to create a compound machine.
Since our last class was before winter break, I started out with a quick review of the six simple machines (wheel and axle, lever, screw, pulley, inclined plane, and wedge). We also reviewed the definition of a machine.
Pulley: A pulley is a wheel with a grooved edge over which a rope can be pulled. There are actually three types of pulleys: Fixed pulleys, movable pulleys, and pulley systems.
Fixed pulleys: Fixed pulleys change the direction of force.
Movable pulleys: Movable pulleys change the amount of force.
Fixed and Movable Pulleys lab: This lab required us to set up a fixed pulley and then a movable pulley and see which one required less force to lift a load (40 coins). The students started out lifting the load with no pulley and discussing their results. We then created the fixed pulley and each student had a turn using the machine to lift the load. To finish, we set up a movable pulley and tried the experiment one more time. We found that the force needed to lift the load with no pulley was the same as that needed to lift the load with a fixed pulley. The movable pulley required a little less force.
Pulley systems: Pulley systems are a combination of both a fixed pulley and a movable pulley. Therefore, they change both the direction and amount of force.
Pulley Systems lab: We used the same load (40 coins) for this lab and started out measuring how much force was required to lift the load with no pulley. We then set up a pulley system with a fixed pulley and a movable pulley. The students then measured the force needed to lift the load using the pulley system.
As predicted, this machine used less force to lift the load than using no pulley. The pulley system required less force than the fixed pulley but about the same amount of force as the movable pulley. However, a pulley system can be more useful since this machine allows a user to pull down rather than lifting up (as was required with the movable pulley).
Compound machines: A compound machine is created when two or more simple machines work together.
Compound Machines lab: For this lab students used household objects to create a windlass, a machine that helps pick up heavy items. The simple machines used to create the windlass are the screw and the wheel and axle. Lab directions can be found here:
http://www.ehow.com/how_4687302_make-compound-machine.html#ixzz13nDbtMRw
*I had a really hard time finding wire hangers but was able to break the hook part from plastic hangers. I just wrapped a little electrical tape around the sharp end of the hook where it had been broken from the hanger.
The Fixed Pulley, Movable Pulley, and Pulley Systems labs were all from a Lakeshore Learning Science Activity Tub on Simple Machines.
The Compound Machines lab was found on this website:
http://www.ehow.com/how_4687302_make-compound-machine.html#ixzz13nDbtMRw
This was our final class for the Fall 2010 semester. Our next Vista Learning Center class session will begin on or around Wednesday, February 23rd. We will hold classes on Wednesdays and Thursdays.
Look for information about class offerings and times to be sent via e-mail.
Hope to see you then!
