With the steel washer immersed in the water the triple-beam balance measures the mass of the washer to be less than its mass is out of water. Obviously, the amount of matter that the steel washer is made up of (which is its mass) does not change by placing it in water. Explain why the triple-beam balance records a smaller mass.

This is because of force of buoyancy experienced by the washer in upward direction from water in which it is immersed. as the steel washer is immersed in water , it displace water equal to its volume. the displaced volume of water apply buoyancy force on the steel washer in upward direction.

due to upward buoyancy force , the effective weight of the steel washer becomes smaller and hence the balance notes a lower value of mass.

It can be said that the washing machine experiences a buoyant force whose direction is upwards, thanks to the water in which it is immersed. When the washer sinks into the water, the volume of water it moves is equal to its volume, also in an upward direction and due to the buoyancy force on the washer. As a consequence of the upward buoyancy force, the effective weight of the washer becomes smaller and, thus, when weighing, a lower mass value can be observed on the balance.

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