The mass of an object that weighs 49 N on Earth is 5 kg. Using the weight equation W = mg and Earth’s gravitational acceleration of 9.8 m/s², rearrange the formula to m = W/g: 49 N ÷ 9.8 m/s² = 5 kg.
This calculation highlights the difference between weight and mass. Weight is a gravitational force and is measured in newtons; mass measures the amount of matter and inertia in an object and is measured in kilograms. On Earth, the two are proportional because the local gravitational field is fairly consistent.
The result would change if the object were moved to another world. A 5 kg object would have much less weight on the Moon, where surface gravity is about one-sixth of Earth’s, but its mass would remain 5 kg. Mass does not depend on the strength of gravity.
The given 49 N is a rounded value. With standard gravity, 5 kg has a weight of about 49.03 N, which rounds to 49 N. The tempting answer “49 kg” confuses newtons with kilograms.