Question 1:

Archimedes’ Principle and Finding Upthrust

Archimedes’ Principle states that:
“When a body is completely or partially immersed in a fluid, it experiences an upward force equal to the weight of the fluid displaced by it.”
This upward force is called upthrust or buoyant force. It acts opposite to the weight of the object and helps objects float or feel lighter in water.

This principle explains why heavy ships float, why objects feel lighter underwater, and why some bodies sink while others rise to the surface. The amount of upthrust depends only on the volume of fluid displaced and the density of the fluid, not on the weight of the object itself.

Finding Upthrust Using Archimedes’ Principle (Detailed Example)

To find the upthrust acting on an object, we measure how much weight the object loses when immersed in water. This loss in weight is equal to the upthrust.

Step-by-step Example:

Suppose we have a metal block.

1. Measure weight in air:
   Let the weight of the block in air be
   W₁ = 50 N

2. Measure weight when fully immersed in water:
   When we put the block completely inside water, the spring balance reading becomes:
   W₂ = 32 N

3. Calculate loss in weight:
   Loss in weight = Weight in air – Weight in water
   Loss = W₁ – W₂
   Loss = 50 N – 32 N = 18 N

4. According to Archimedes’ Principle:
   Upthrust = Loss in weight = 18 N

This means water pushes the block upward with a force of 18 N, which is why its weight appears reduced when immersed.

Conclusion

Archimedes’ Principle helps us calculate upthrust by simply finding the difference between the weight in air and the weight in fluid. The upthrust equals the weight of the water displaced by the object. This principle is essential in understanding floating, sinking, designing ships, submarines, hydrometers, and many fluid-related application