Patterns in Motion

Once students understand how wind provides an unbalanced force that moves a windmill’s blades, they focus on the patterns formed by the windmill’s motion. Specifically, in this lesson, they predict how the movement of the rotor will change when the mass of the windmill blades changes.

• Scientists can use patterns in where the wind is strongest to decide where to build wind farms.
• There are patterns in motion all around us. We can use these patterns to make predictions about future movement.
  
  

• Why do people need to think about where in the world they are going to build a windmill?
• Why does a stronger wind with more kinetic energy cause windmill blades to move faster than a lighter wind?
• What causes a person on a swing to start to move?
• How does a swing move in a predictable way?
• Why will a swing eventually slow down?
• Why don't people all swing at the same height and speed, given that the motion is so predictable?
• Why does an adult move less far than a child when both are pushed on the swing with the same amount of force? How could an adult swing as fast and as high as a child?
  
  

Misconception: If an object is at rest, there are no forces acting on it.

Fact: There are forces everywhere. When an object is at rest, all of the forces acting on it are balanced.

Misconception: A force is necessary to keep an object moving.

Fact: An unbalanced force changes an object’s motion. An object that is already in motion will continue moving until acted on by an unbalanced force, such as friction.

Misconception: Only moving objects have energy.

Fact: Nonmoving objects have stored potential energy.

Balanced : when all of the forces acting on an object are equal

Friction : a force that slows motion whenever two objects rub against each other

Kinetic Energy: energy of motion

Potential Energy : energy that is stored

Unbalanced : when the forces acting on an object are not equal

Wind : moving air molecules

Windmill : a structure that captures the wind’s kinetic energy to do work

Work : any change in position, speed, or state of matter due to force

Patterns in Wind

The state of California is home to the largest wind farm in the United States. A wind farm is made up of a kind of windmill called a turbine. Wind turbines capture the wind’s energy to produce electricity.

The California wind farm is located in the mountains. Mountains are very windy. Coastlines along the ocean are also very windy.

Remember that the stronger the wind is, the more kinetic energy it has. People build windmills in places that they know are windy. This is because windmills in windy places are able to do more work.

Predicting Motion

There are patterns in how a windmill moves. There are patterns in motion all around us. These patterns can be used to make predictions about future movement. For example, when you move back and forth on a swing, your motion follows a predictable pattern.

First, you cannot move on the swing unless an unbalanced force causes you to move. This can come from someone else pushing you, or pushing off the ground with your feet.

Once you are in motion, the swing moves back and forth in a predictable way. It will take the swing the same amount of time to complete each swing. You will keep moving like this until another force slows you down. For example, air resistance will slow you down. Air resistance is similar to friction. It turns motion energy into heat.

In this lesson, students investigate the motion of windmill rotors when there are differences in blade design. Students compare the number of times the windmill rotor turns in 10 seconds under different designs. Students gather quantitative data on the number of times the rotor turns. They then organize their data in a data table to observe any patterns that suggest a cause-and-effect relationship between the mass of the blades and the amount of work the windmill can do.