Question

A beaker containing water is placed on the platform of a spring balance. Tha balance reads $1.5\text{kg}$. A stone of mass $0.5\text{kg}$ and density ${10}^4{\text{kg/m}}^3$ is floats in water without touching the walls of the beaker. What will be the balance reading now (in $\text{kg}$)?

Answer 1

According to Newton's third law, as the water exerts upthrust on the stone, the stone also exerts the same force on water.
Upthrust force acting on the stone should be balanced by its weight, as stone is floating.


Also, the weight is exerted on the beaker. Therefore the reading will be $1.5+0.5=2\text{kg}$