Weight and Mass

1
Weight and Mass

• Are they the same thing?

2

• Most people say the words weight and mass as if
  the mean exactly the same thing. They do not.
• Think about an astronaut in outer space who is
  weightless, but definitely has mass.

3
Mass

• Mass refers to the amount of matter, or stuff, in
  an object.
• A 46 gram rock will always have a mass of 46
  grams, whether on Earth, the Moon, or anywhere
  else in outer space.
• The properties of mass are constant.
• In the metric system it is measured in kilograms.

4
Weight

• The weight of an object depends on the strength
  of gravity pulling on it and is a measure of the
  force of that pull.
• So, weight measures the gravitational attraction
  between two objects.
• Weight varies with location. A 24 pound rock on
  Earth would only weigh 4 pounds (1/6th as much)
  on the Moon.
• Weight is measured in Newtons in the metric
  system.

5
Traveling through space

• Imagine a person on the Earth who has a mass of
  45 kilograms.
• What would be their mass on the Moon, Mars,
  Jupiter, Pluto or the Sun?
• Hint Mass in constant
• The mass would always be 45 kilograms

6
What about weight?Imagine a person who weighs
100 lbs on Earth.

• On the Moon this person would have a weight of
  16.6 lbs.
• On Mars, 37.7 lbs.
• On Jupiter, 236.4 lbs.
• On Pluto, 6.7 lbs.
• On the Sun, 2,702.2 lbs.
• Weight varies with location based on the pull of
  gravity on the object.

7
FCAT Question

• Brianna and Eldon watched a videotape of an
  astronaut floating in outer space. Brianna said
  that in space the astronaut had no weight or
  mass. Eldon said that the astronaut had mass,
  but no weight. Who was correct? Explain and
  include a definition of both mass and weight in
  your answer.

8
Discussion

• Eldon was correct when he said that the astronaut
  in outer space had mass, but no weight. The
  astronaut in space had the same mass as on Earth.
  The weight, however, was nearly zero because the
  astronaut was so far from Earth.

9
Work Cited

• Zweig, Steven (2002). FCAT Science Coach, Grade
  8. New York, N.Y. Triumph Learning.