Finding mass

The idea

Mass can be measured indirectly by measuring weight with a spring balance or by comparing weight with that of a known mass on a beam balance, since weight is almost the same everywhere on Earth.

How much matter

Mass is the amount of matter in an object.

How could you find the mass of an object?

• Compare it with known masses on a balance
• Look at its colour
• Smell it

Balance the beam

Add known masses to the right pan until the beam is level.

Weigh to find mass

The beam was level when the known masses weighed as much as the object. On the Earth the weight of an object is almost the same everywhere, so we can weigh an object to find its mass.

We can measure mass indirectly: by measuring the object's weight with a spring balance, or by comparing its weight with that of a known mass on a beam balance. Weight is almost the same everywhere on the Earth, so this is acceptable.

Notes

Mass can be found by measuring weight with a spring balance, or by comparing weights on a beam balance. Weight is almost the same everywhere on the Earth.

Check yourself

The beam balance is level. The object and the known masses …

The object balances 3 kg of known masses (an example). What is its mass?

Answer: 3 kg

Its mass is 3 kg.

We can measure the mass of an object indirectly by …

Why can we weigh an object to find its mass on the Earth?

• have different weights. A level beam means both sides pull down equally.
• are the same colour. Colour has nothing to do with it.
• have the same weight — correct. Yes!
• measuring its weight — correct. Yes!
• measuring its colour. Colour does not give the mass.
• measuring its shadow. The weight gives the mass.
• Mass and weight are the same thing. They are different. But the weight is almost the same everywhere on the Earth.
• Weight is almost the same everywhere on the Earth — correct. Yes!
• Because mass keeps changing. Mass does not change. The weight is almost the same everywhere on the Earth.