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P199: Weight vs. Mass

P199: Weight vs. Mass. Lecturer Stacy McCormack Physics Department, Indiana University. They both appear to be objects with a fixed “heaviness” that we can measure on a scale. Aren’t they the same thing?.

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P199: Weight vs. Mass

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  1. P199: Weight vs. Mass Lecturer Stacy McCormack Physics Department, Indiana University

  2. They both appear to be objects with a fixed “heaviness” that we can measure on a scale. Aren’t they the same thing? But mass and weight are two COMPLETELY DIFFERENT QUANTITIES OR CONCEPTS that are quite often confused. 1 lb = 454 grams = 0.454 kilograms = 4.45 N

  3. Definition: The measure of the amount of matter an object contains. matter=“stuff” Unit: grams or kilograms (1 kilogram = 1000 grams) We call these “masses” because we have measured the precise amount of matter in grams that each one contains. Mass The mass of an object depends only on what is INSIDE the object.

  4. Definition: The measure of how strongly gravity pulls on an object. Units: pounds (US), Newtons (metric). 1 lb = 4.45 N • Weight depends on two factors: • Mass: the greater the mass, the greater the weight. • Gravity: the greater the gravity, the greater the weight. These “weights” are measured in pounds. Weight So whereas mass is determined by something inside the object, weight is determined by something OUTSIDE the object…gravity!

  5. Weight in Newtons = (Gravitational factor) * (Mass in kilograms) Gravitational Factor

  6. http://www.exploratorium.edu/ronh/weight/ Your weight on other worlds

  7. To do this, we can use the conversion we learned a few slides ago… 1 lb = 454 grams = 0.454 kilograms Example #1-Mass on Earth Since the weight given was ON EARTH and the mass we were finding was ON EARTH, there was no need to use a gravitational factor. The gravity didn’t change.

  8. 61.29kg . Example #2-Jupiter or bust! TRICK QUESTION…WATCH FOR THIS!!! MASS NEVER CHANGES…ONLY WEIGHT!!!

  9. Compare and predict… will your weight on Jupiter be MORE or LESS? Because Jupiter has a stronger gravity than the Earth, we expect that your weight has increased. Example #3-WEIGHT on Jupiter

  10. …to put the 26.4 on the top and the 9.8 on the bottom? If I know that my weight will increase (higher gravitational factor on Jupiter than on Earth-gravitational factor increases), then I needed to put the larger number in the numerator. However…if in the future I know that the weight will decrease (gravitational factor decreases), then I need to put the larger number in the denominator. How did I know…

  11. A box on Earth has a weight of 20 lbs. What is the weight on the moon? QUICK CHECK: Gravitational factor DECREASED. Weight DECREASED. Looks great! Example #4-To the moon!

  12. Motion on the Moon-1969 Why does walking look different? Because of GRAVITY. Less gravitational factor on the moon, less weight. Less weight, motion appears and feels different.

  13. Example #5-Motion on Moon Check…how did I know that the 9.8 went in the denominator???

  14. 1 lb = 454 grams = 0.454 kilograms = 4.45 N MASS NEVER CHANGES…ONLY WEIGHT!!! If gravitational factor increases, then weightshould increase…so the larger gravitational factor goes in the NUMERATOR. If gravitational factor decreases, then weight should decrease…so the larger gravitational factor goes in the DENOMINATOR. If gravitational factor increases, then time and distanceshould decrease…so the larger gravitational factor goes in the DENOMINATOR. If gravitational factor decreases, then time and distanceshould increase…so the larger gravitational factor goes in the NUMERATOR. Weight vs. Mass Review Weight in Newtons = (Gravitational factor) * (Mass in kilograms)

  15. The “Vomit Comet”

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