Gravity and Weight on Different Celestial Bodies

Weight of Box on Earth

I invite you to test science activities and experiments for me. If you are interested, you can contact me directly at ASKJANICE@aol.com

To give you a clue of what to expect, the following activity was field tested by Shay Arnold and her children. I emailed the activity with pictures to her. She and her children completed the activity and Shay let me know which parts worked best for each age as well as which parts were not clear. As a results of her input, I can now present to you a much better version of the activity. So let’s get started!

Did You Know?

A celestial body is any and all objects making up the universe. These include, planets, moons, suns, comets, stars, asteroids, etc….

Earth and its Moon are both celestial bodies.

Measuring the Earth’s Gravity

1. Your weight is the measure of the force of Earth’s gravity pulling you down.
NOTE: Down is the vertical direction toward the center of the Earth.

2. Weight on Earth, Fw = Force of Earth’s gravity, Fg
This means that when you stand on the bathroom scales, you are measuring the force of Earth’s gravity pulling you down .

Weight = Force of Gravity
Fw = Fg

Force of Gravity = Weight
Fg = Fw

The black box in Diagram A has a weight of one pound on Earth. This means that Earth’s force of gravity pulling the box down is equal to one pound.

Pound is a unit used to measure force.
Pound is a unit used to measure weight.

Measuring the Moon’s Gravity

Weight On the Moon

Let’s pretend that you can snap your fingers and send the box in Diagram A to the Moon.

Question: How much would the box weigh on the Moon?

REMEMBER: Weight is a measure of the force of gravity pulling an object down.

Answer: The gravity of the Earth’s Moon is about 1/6 as much as Earth’s gravity. This means that the weight of the box would be 1/6 of its weight on Earth. Thus the box’s weight is 1/6 pound.

Math Enrichment: 1/6 x 1 pound= ??  (Divide 1 by 6 = 0.167 pounds)

Investigation:

1. How much do you weigh on Earth?

Examples: Bret- 100 lbs. Bree and Brittan= 50 lbs.

2. How much is the force of Earth’s gravity pulling your body down?

Remember: Fg = Fw

Example:
1. Bret:
weight = 100 lbs; Earths’s force of gravity pulling down on Bret = 100 lbs.
2. Bree and Brittan: weight = 50 lbs;  force of gravity pulling down on Bree and Brittan= 50 lbs

3. If you could snap your finger and be on the Moon, how much would you weight?

Example: Bret= 16 lbs Bree/Brittan= 8 lbs

4. How much is the force of the Moon’s gravity pulling your body down?

Example:
Bret: weight =16 lbs; Moon’s force of  gravity pulling down on Bret= 16 lbs

Bree/Brittan:= 8 lbs; Moon’s force of gravity pulling down on Bree and Brittan = 8 lbs

Did You Know?

I rode in NASA’s training and investigation plane commonly called “The Vomit Comet.” For information about my “weightless” investigation, click    HERE.