Understanding the Concepts

* Relative Density: The relative density of a liquid is the ratio of its density to the density of water.

* Buoyancy: When an object is submerged in a fluid, it experiences an upward force called buoyant force. This force is equal to the weight of the fluid displaced by the object.

* Apparent Weight: The apparent weight of an object submerged in a fluid is its actual weight minus the buoyant force.

Solution

1. Find the volume of the solid:

- The apparent weight of the solid in the liquid is 40 N. This means the buoyant force acting on it is equal to the difference between its actual weight and its apparent weight. However, we don't know the actual weight.

- We need to use the relative density to find the volume.

- Let the density of water be ρw and the density of the liquid be ρl.

- Relative density (RD) = ρl/ρw = 0.8

- Since we know the density of water is 1000 kg/m³, we can calculate the density of the liquid:

ρl = 0.8 * ρw = 0.8 * 1000 kg/m³ = 800 kg/m³

- We still need more information to find the volume.

2. Find the weight of the water displaced:

- The weight of the water displaced is equal to the buoyant force acting on the solid.

- We need the volume of the solid to calculate the weight of the water it displaces.

Conclusion

We can't determine the weight of the water displaced without knowing the actual weight of the solid or its volume.

To complete the problem, you would need additional information like:

* The actual weight of the solid: This would allow you to calculate the buoyant force and then the weight of the water displaced.

* The volume of the solid: This would directly allow you to calculate the weight of the water displaced.