We learned that a pendulum is a weight that hangs from the end of a rope, wire, or string in motion. One end of the wire is attached to a fixed point. In our lesson students made a pendulum with a 7 inch string with a donut, and watched it swing three cycles. One student was a timekeeper and another student recorded the time it took the pendulum to swing in three cycles. Students then changed the length of the string to 5 inches and recorded how long it took the pendulum to swing for three cycles. Again, students recorded their data and compared the data from this one changed variable (the length of the string). What patterns did you notice?
Click on the link below to view the experiment:
Now that we found through our experiment that changing the length of a pendulum changes the time it takes to complete a swing; the shorter the pendulum, the faster it swings.
You can continue to explore with the applet below to change another variable. Maybe you will change the amount of friction or the amount of gravity. Remember to only change one variable at a time to have a fair test method. Have fun and experiment with the applet and remember to find patterns with the pendulum. Here are some questions to reflect about while exploring:
- What makes a swing similar to a pendulum?
- Why do you need to push and pump to get yourself going in the first place?
- What makes you (or any pendulum bob) keep coming down to the ground and not flying off into the air?
- What makes you (or any pendulum bob) keep going up? ) Hint:.TAKE AWAY FRICTION (force) see what happens.
- How could we change the rate of the pendulum swing?
***Here is an applet that shows a pendulum that you can virtually manipulate. You will need to download this.
You can lengthen or shorten the string, add friction, add more or less gravity.