What is the difference between mass and weight? Weight is the effect of gravity on an object. Mass is the amount of matter in an object regardless of the effect of gravity on the object. If you moved the flagpole to the Moon, its weight would be reduced by about 5/6 of its weight, but its mass would remain the same.
Step
Method 1 of 2: Changing Weight and Mass
Step 1. Know that F (force) = m (mass) * a (acceleration)
This simple equation is what you'll use to convert weight to mass (or mass to weight, if you prefer). Don't worry about the meaning of the letters – we'll tell you:
- Force is the same as weight. Use Newtons (N) as the unit of weight.
- Mass is what you're looking for, so it might not be defined in the first place. After solving the equation, your mass will be calculated in kilograms (kg).
- Acceleration is the same as gravity. Gravity on the earth is constant, which is 9.78 m/s2. If you measure gravity on another planet, this constant will be different.
Step 2. Convert weight to mass by following this example
Let's illustrate how to convert weight to mass using an example. Suppose you are on earth and trying to find out the mass of your 50 kg soapbox race car.
- Write down your equation. F = m * a.
- Fill it with your variables and constants. We know that force is the same as weight, which is 50 N. We also know that the gravitational force on the earth is always 9.78 m/s2. Enter both numbers and your equation should look like this: 50 N = m * 9, 78 m/s2
- Rearrange the order to complete. We can't solve the equation like this. We need to divide 50 kg by 9.78 m/s2 to be alone m.
- 50 N / 9, 78 m/s2 = 5.11 kg. A soapbox racing car that weighs 50 Newtons on earth has a mass of about 5 kg, wherever you use it in the universe!
Step 3. Convert mass to weight
Learn how to convert mass back to weight using this example. Suppose you pick up a moonstone on the lunar surface (where else?). Its mass is 1.25 kg. You want to know its weight if it is brought back to earth.
- Write down your equation. F = m * a.
- Fill it with your variables and constants. We have mass and we have the gravitational constant. We know that F = 1.25 kg * 9.78 m/s2.
- Solve the equation. Since the variable we're looking for is already on one side of the equation, we don't need to move anything to solve the equation. We only need to multiply 1.25 kg by 9.78 m/s2, becomes 12, 23 Newtons.
Method 2 of 2: Measuring Mass Without Equations
Step 1. Measure the gravitational mass
You can measure this mass using a balance. A balance differs from a scale in that it uses a known mass to measure an unknown mass, whereas a scale actually measures weight.
- Finding mass with a three-arm or two-arm balance is a form of measuring gravitational mass. This is a static measurement, which means that it is only accurate if the object being measured is at rest.
- The balance can measure weight and mass. Since the measurement of the weight of the balance changes according to the same factors as the object being measured, the balance can accurately measure the mass of an object regardless of the specific gravity of the environment.
Step 2. Measure the inertial mass
Inertial mass is a dynamic way of measuring, meaning that this measurement can only be made if the object being measured is moving. Object inertia is used to measure the amount of a substance.
- An inertial balance is used to measure inertial mass.
- Place the inertial balance on a table.
- Calibrate the inertial balance by moving the case and counting the number of vibrations in a certain time interval, for example 30 seconds.
- Place an object of known mass in the container and repeat the experiment.
- Continue using several objects of known mass to complete the calibration of the scale.
- Repeat the experiment with an object of unknown mass.
- Graph all the results to find the mass of the last object.
Tips
- The mass of an object does not change even though the method of measuring it is different.
- The inertial balance can be used to find the mass of an object even in a 0 gravity environment.
