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Weight and Mass

Sometimes people use the words weight and mass to mean the same thing. This, however, is not really accurate. Weight is related to mass, but it is not the same. Scientists measure weight using a unit called the Newton (N). Usually we refer to weight in pounds and ounces here in Utah. Weight is a measure of the force of gravity on an object.

Mass is the amount of matter in an object and does not change with location. Scientists measure mass using a unit called the gram (g). If an object is moved to a location of greater gravitational force, such as Jupiter, its weight will increase, but it’s mass will remain the same. The only way to change the mass of an object is to take away part of the object or add to it.

An object with a mass of one kilogram has the same mass on another planet, like Jupiter. However, because Jupiter is larger, the weight of the object would be different. In other words, the two planets would exert a different gravitational force on the same object.


Look closely at the images below. The same scientist is seen in each image. The comparisons between weight and mass here are based on data from the Earth and its moon.

Visit the Exploratorium to determine what you would weigh on the other planets of our solar system.


  1. What is the mass of the scientist?
  2. Which of these two objects is exerting the greater gravitational force - the Earth or its moon?
  3. Which is a more accurate measurement - mass or weight?
  4. How can you change your mass?

Review Science safetey rules here.

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  1. The title of the activity
  2. The URL (Internet address)
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Teachers should view the Teacher Site Map to relate Sci-ber text and the USOE 8th grade science core.

Updated October 24, 2008 by: Glen Westbroek

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