1. Mass and Weight

2. Mass Mass is the amount of matter in a given object Anything made up of matter has mass We all have mass, whether it’s Sunday or not and whether we happen to be Catholic or not.

3. Weight Weight is a sensation of force we get as we press against other objects. You press against a scale to measure your weight. What pulls you against the scale?

4. Gravity! Gravity keeps trying to accelerate us toward the earth and we get pressed against things. This gives us the feeling of weight. Our perception of weight can be altered by our environment. WHAT?

5. That’s Right Our perception of weight may be different in different circumstances. What about if you’re on the moon?

6. The moon has less mass, therefore less gravity associated with it. There is less attraction between your body and the moon. The moon pulls on your body less than the earth… SOOOO… you would press down on a scale with less force. Your weight on the moon would be about 1/6 of your earthly weight.

7. We feel weight as a force! You typically measure your weight in pounds (lb) In the metric system (SI), weight is measured in newtons (N) Here is something you need to know… 4.45 N = 1 lb. ALSO…

8. Since weight is a product of mass and gravity the equation for calculating weight is… w = mg

9. Weight in newtons Acceleration of gravity, symbolized by “g” is equal to … 9.8 m/s 2 At or near the earth’s surface, gravity tries to accelerate objects 9.8 m/s faster each second Mass in kg

10. N = kg x 9.8 m/s 2 weight mass acceleration of gravity (g)

11. Gravity …. again So… remember that we said weight is a sensation that we experience when we are forced against something. Knowing that, ponder these next questions: 1)What does it mean when it is said that we are “weightless” in space 2)If Earth has a given mass and you have a given mass, how can you be weightless? 3)Have you ever heard of “multiple g forces”? Along the same line as question #2, how can you experience that phenomenon? 4)What happens to the force of gravitational attraction as two objects move farther apart? 5)What happens to the force of gravitational attraction as the mass of either or both of two objects increases? Gravity 09.doc Click on the document link below and read it