(Before you start, have a chair with wheels or a skateboard sitting in a
corner of the room.)
1. Have the RISE girls and you, their leader, sit in the middle of the floor cross-legged style. Tell the girls that you want the strongest girl in the group to try and move you across the room.
(Leaders be prepared to lock your arms around yourself or bend into a
ball like shape. Allow the girls to try to pull or push you across the room,
but resist moving. 
However, if they succeed in pushing you across
the floor, just stay wherever you end up.)
Allow the girl approximately 2 - 3 minutes to attempt to push/pull you before she sits down.
2. Ask another girl to try to move you across the room, and continue until a number of the girls have tried. (Or until you are tired.)
NOTE: You might have a girl who will figure out that it will be easier for her to roll you like a log; that's O.K., just continue. What they have discovered is the earliest wheel and the principle that machines make work easier.
3. Ask the girls if trying to move you was easy. Also, ask them to describe what they were doing to try to move you. Try to lead them into using the words PUSH and PULL as part of their explanations.
4. Tell the girls that PUSH and PULL are types of FORCES. The girls were using the forces of PUSH and PULL when they moved you. This use of force is called EFFORT. The effort they used when they moved the leader is called WORK. Work occurs when you have a force that creates movement.
5. Have the girls talk about other times they had to work using the Physics definition of work.
6. Ask the girls if they can find something to use in the room that could be used to help them move you across the room. Lead the girls into suggesting putting you in the chair with wheels. Allow the girls to ask you to sit in the chair. The girls then can wheel you easily across the floor.
7. Discuss with the girls which was easier, using the chair or not using it. They have discovered that a machine's main purpose is to reduce the force necessary to do work.
A FORCE is an influence on an object that changes its shape or position. There are many types of forces, such as gravity,which is a pulling force and rocket thrust, which is a pushing force.
PUSH is when the force is applied directly to an object, whereas PULL is where the force is used to draw in the object.
EFFORT FORCE is the force applied to a machine, when a machine is used to produce work.
WORK is the transfer of energy through motion; work=force x distance.
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