# Little Johnny and his Pet Cow

Name of Activity

Little Johnny and his Pet Cow

Author

Matthew Mueller

Keywords

Pulleys, simple machines, weighing, balancing, well

Subject

Simple Machines

3, 4, 5, 6, 7

Time

1 Hour Total

Brief Description

Little Johnny’s pet cow has fallen down a well! You need to come up with a system of pulleys that will help little Johnny lift his cow out of the well.

Lesson Objectives:

Get kids to understand the idea that pulleys can both change direction of motion, and lessen the amount of force needed to lift a heavy object.

Materials Needed:

Lego pulleys, beams, axles, string, weights

Necessary Background

A basic understanding of pulleys and their uses.

Procedure

First have the kids try and make a wall of pulleys and show how it is easier to pull up a heavy object when using the pulleys.  Then challenge the kids to build a wall of pulleys that is capable of balancing as many weights on one side with just one weight on the other side.

Extensions:

They can always try to balance more weights on one side and show that the more pulleys there are, the lighter the load will seem on the other side.

Umbrella Unit/Curriculum (if applicable)

Simple Machines

You must be