Final answer:
The up thrust on the stone is 20 Newtons, calculated by subtracting its weight in water (60N) from its weight in air (80N).
Step-by-step explanation:
The question is asking to calculate the up thrust, also known as the buoyant force, acting on a stone when it is immersed in water. To find the up thrust, we need to use the fact that the apparent loss in weight of the object when submerged in water is equal to the up thrust. The formula to calculate the up thrust (Buoyant Force) is the difference between the weight of the stone in air and the weight of the stone in water.
We have the stone's weight in air which is 80N, and its weight in water which is 60N. Therefore, the up thrust is:
- Up thrust = Weight in air - Weight in water
- Up thrust = 80N - 60N
- Up thrust = 20N
The up thrust or the buoyant force on the stone is 20 Newtons.