weight

Weight is the force of gravity pulling an object toward a planet or other large body.

• On Earth, gravity pulls each kilogram of mass with a force of about 10 newtons. So a 2 kg school bag has a weight of about 20 N.
• Scientists write this relationship as weight = mass × gravitational field strength. Near Earth’s surface, the gravitational field strength is about 10 N/kg.
• A spring balance measures weight because a stronger pull stretches its spring more. The spring is calibrated so that each amount of stretch matches a force in newtons.
• Your mass stays the same if you travel to the Moon, but your weight becomes smaller there because the Moon’s gravity is weaker. You would not lose any matter—gravity would simply pull on you less strongly.

Weight helps us describe how strongly gravity acts on an object, which is important when measuring forces, designing vehicles, or planning space travel.