Remember a simple machine doesn’t change the amount of work you do. You will still move an object the same distance. What a simple machine does is make that work take less effort. Are rollers a simple machine? What are rollers anyway?
These are not the kind girls use to curl their hair.
Question: How do rollers work?
String (scissors to cut it)
Six or seven round pencils
Wrap the string one and a half times around the book
Cut off the piece of string
Tie a loop in one end of the string
Put the other end of the string through the rubber band and the loop
Pull the string tight
Tie the string around the book
Use the rubber band to pull the book across the table
Set the book back at the beginning
Space out the pencils so three will be under the book and the others in front of it
Set the book on the last three pencils
Use the rubber band to pull the book across the pencils
Describe how the rubber band behaves as you pull the book on the table
Describe how it feels pulling the book on the table
Describe how the rubber band behaves as you pull the book across the pencils
Describe how it feels pulling the book across the pencils
Assuming you pulled the book the same distance both times, did you do the same amount of work? Why do you think so?
Was it easier to pull the book on the table or on the pencils?
What did the pencils do under the book as it went over the top of them?
Why would the pencils be called rollers?
Can you think of another name for a roller? What is it?
What I Found Out:
My book had a slick book cover on it so it pulled across the table easily. The rubber band stretches out at first then sprang back once the book started moving. The book dragged a little on the table.
The rubber band barely stretched before the book started pulling over the pencils. It moved very fast over the pencils. The book didn’t drag at all.
Since work is the distance times the mass, I did the same amount of work. The mass of the book and the distance did not change with and without the pencils.
What did change is how easy it was to pull the book over the pencils. The pencils turned and rolled under the book.
The pencils could be called rollers because that is what they did: rolled. Something else that rolls is a wheel.