Forces and Motion 6 th Grade Unit Becky Berg

What is Gravity? Gravity is the word we use to describe the pull between masses. Things with more MASS produce a greater Gravity pull on each other.

A Little Song About Gravity Click on the music note to hear the gravity song!

Gravity controls…. A roller coaster’s ride A diver’s dive A skier’s jump A baseball’s fall

What word describes how much of you there is?

Mass Your mass is the amount of material that your body contains. How can you gain mass? I’d eat a looott of yummy bread to gain mass!

Does something that is bigger always have more mass?

Does bigger= more mass?

So, having more mass does not mean taking up more space!

Mass vs. Weight Do things that have more mass always weigh more?

When you stand on a bathroom scale, the scale is made of springs. The farther down you push the springs, the higher the number on the scale. The number tells you your weight. On earth it is true that the more mass you have, the more weight you have.

Weight? Mass? I am totally confused!

Pretend That You Are in Space! You are floating around. You drift over to a floating bathroom scale and put your feet on it. Your feet do not push down on the scale at all. The scale shows that you weigh 0. You have lost your weight—but did you lose your mass? Oh where, oh where, has my weight gone? Oh where, oh where can it be?

All my body parts are still together—so I still have mass!

On a space flight, your mass would be the same; but your weight would change.

Summing up Mass and Weight Your MASS is the amount of material in your body. Your MASS doesn’t depend on where you are. Your WEIGHT is how much your body pushes down on a scale. Your WEIGHT depends on how much MASS you have and where you are.

Where would you weigh the most? Earth Moon OR

Remember, gravity describes the pull between masses. You have mass, and the earth has mass. There is a pull between you and the earth. We measure this pull with a scale. The more the gravity, the greater the squeeze on the springs of the scale…and the more you weigh.

Gravity and Weight Summary Your weight on earth is a measure of the GRAVITY pull between you and the earth. Bodies with more MASS produce a greater GRAVITY pull on each other.

On Earth So, if I ate a lot of yummy tuna fish while standing on the scale, I would gain mass. The pull between the earth and me would become greater—and I would weigh more!

Back to the Moon During my trip to the moon, my mass does not change, but the moon has much less mass than the earth.

Still on the Moon! There is less gravity pull between you and the moon. If you stood on the scale on the moon—you would weigh less than on earth!

Imagine…..