Levers and Launchers

Author: Maddie Van Beek

Today, we are exploring the concepts of levers and fulcrums. You are going to create a simple machine that contains both a lever and a fulcrum--a ping-pong ball launcher! Before we get started, you need to know a little bit about what a lever is and what a fulcrum is.


First of all, what is a simple machine?


Think about what a machine does. There are so many different machines out there, but the main purpose behind machines is that they make life easier for people. Simple machines make work (the force acting on an object in the direction of motion) easier for humans to complete.


A simple machine could be any of the following:


* Wheel and axle
* Lever
* Inclined plane
* Pulley
* Screw
* Wedge


Read more about the six simple machines that make work easier (http://www.livescience.com/49106-simple-machines.html).


The simple machine you’re creating today is a lever.


A lever contains both a beam and a fulcrum. The fulcrum is the pivot of the lever. Think about levers in your everyday life. When have you seen a lever? One example is a seesaw... the bench that the two people sit on is the beam, while the center piece holding the beam in place is the fulcrum.

http://assets.cedarworks.com/assets_img/rwd_playsets_main/originals/backyard_seesaw.jpg

Fulcrum: The point at which the lever rests, is supported, and pivots.


Lever: A bar or beam resting on a pivot. Pressure (force) is applied to one end to help move an object (load) on the other end.


Check out the diagram of a lever below. You can see the beam resting over a pivot, which is the fulcrum. When you think of the ping-pong ball launcher you are about to create, the force will be you pushing down on the lever, and the load will be the ping-pong ball.

http://combatlab.russianmartialart.org.uk/userfiles/images/1st%20class%20lever%20diagram.jpg

Now that you know a little bit about levers, you can get started on creating your own!


YOU WILL NEED:
* Plastic cup
* Ping-pong balls
* Wooden yardstick
* Tape
* Variety of fulcrums (thick book, shoe box, coffee can, log, etc.)


Here’s what to do!
1. Tape a plastic cup to one end of the wooden yardstick. Make sure you use lots of tape so the cup stays put! Your finished product should look like the shape below. The base of the cup is taped down, and the mouth of the cup is facing up. This is your ping-pong launcher!

2. Select your first fulcrum.
3. Set your your ping-pong launcher over the top of the fulcrum. The launcher should lean to the side over the fulcrum like the shape below.

4. Place the ping-pong in the plastic cup on the lower end of the launcher. Make a prediction, how far do you think the ping-pong ball will fly?
5. Quickly press down on the top end of the launcher to send the ball flying! Use a tape measure to check how far the ping-pong ball traveled. Repeat this five times and record your results each time. After the fifth launch, find the average launch distance. Do this by following the formula below.


Launch 1 + Launch 2 + Launch 3 + Launch 4 + Launch 5 = Total launch distance


Total launch distance / Number of launches


Total / 5 = Average Launch distance


6. How might changing the position of the fulcrum change the launch distance? Try moving the fulcrum closer to the launch cup.

Repeat step 5. What did you notice about the launch distance?


7. Try moving the fulcrum further away from the launch cup. Repeat step 5. What happened this time?

8. Record your conclusion. Which position launched the ball the furthest?


Extension: Now that you know which position works best, try using different fulcrums! Do different sizes or shapes affect the launch distance? Repeat the activity with at least two other fulcrums to determine which works best.


References:
http://buggyandbuddy.com/science-kids-launching-ping-pong-ball-snowmen/
http://www.livescience.com/49106-simple-machines.html