# You weigh 23lbs on Earth. (4.448N=1lb) When you reach Alderon, you discover that its gravity is 1.21that of Earth. What is your weight on Alderon? Answer in units of N

t-nez | High School Teacher | (Level 3) Associate Educator

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If you weigh 23 lbs on earth, your weight in Newtons is:

(23 lbs) X (4.448 N/1lb) = 102.3 N

Since weight = (mass)(acceleration due to gravity), and the gravitational force on Alberon is 1.21 that on earth, your weight on Alberon will be:

(1.21)(102.3 N)= 123.8 N

Mass, which is expressed in kilograms, is the amount of matter something contains and will be the same in any setting. Since weight is the force exerted by mass, it varies depending on the local gravitational force. When we say someone "weighs" 70 kg we are actually expressing the person's mass. The kilogram isn't a unit of weight. On earth, where acceleration due to gravity is 9.8 m/s^2, a person with a mass of 70 kg has a weight of (9.8 m/s^2)(70kg) = 686 N. The pound is a weight unit and takes into account Earth's gravity.

The weight of an object on another planet depends on that planet's gravitational force. In this case we could calculate the weight on another planet by knowing how its gravity compares to Earth's.