Share:
How It Works
Weight is the gravitational force on an object: W = m · g. Unlike mass (which stays the same everywhere), weight changes with gravitational acceleration. On Earth, g ≈ 9.81 m/s²; on the Moon, g ≈ 1.62 m/s². The same 70 kg person weighs 687 N on Earth but only 113 N on the Moon.
Example Problem
What does a 50 kg suitcase weigh on Earth?
- W = 50 × 9.81 = 490.5 N
In everyday terms, that is about 110.2 lbf.
Frequently Asked Questions
What is the difference between mass and weight?
Mass (kg) measures the amount of matter in an object and never changes. Weight (N) is the gravitational force on that mass and varies with location. A 70 kg person weighs less on the Moon than on Earth.
Why do bathroom scales show kilograms?
Scales are calibrated assuming standard Earth gravity. They measure force (weight) but display the equivalent mass. In a different gravitational field, the reading would be wrong.
What is the value of g on other planets?
Mars: 3.72 m/s². Jupiter: 24.79 m/s². Moon: 1.62 m/s². A 70 kg person would weigh 260 N on Mars and 1,735 N on Jupiter.
Related Calculators
- Gravity Equations Calculator — calculate g at different altitudes and for different planets.
- Force Equation Calculator — general F = ma calculations.
- Density Calculator — find mass from density and volume.
- Specific Gravity Calculator — compare substance density to water.
- Mass Unit Converter — convert between kilograms, pounds, ounces, and grams.
Reference: Lindeburg, Michael R. 1992. Engineer In Training Reference Manual. Professional Publication, Inc. 8th Edition.