The actual question is
A copper piece of mass 10g is suspended by a vertical spring. The spring elongates 1 cm over it's natural length to keep the piece in equilibrium. A beaker containing water is now placed before the piece so we to immerse the piece completely in water. Find the elongation of the spring. Density of copper: 9000 kg/m³. Take g= 10 m/s²
I am not sure about the forces and their directions that act on the block after it is in water
In this case the forces acting on the copper piece and their directions can depicted by this simple diagram(Also known as a Free body daigram):
- Gravitational force is acting on the copper block in downwards direction.
- Water is exerting buoyant force on the block in upward direction.
- The spring force is acting upwards too.
Spring force(F=k.Δx) and buoyant force(F=pgV) is being balanced by the downwards pull of gravity(g) to keep the system in stationary equilbrium.
All other minor forces acting on the copper piece can be neglected.
The main forces acting on the block are the force of gravitation acting downward, the restoring force of the spring acting upwards before and downward after it compressed due to the buoyant force, and the buoyant force due to the water pushing the block upward.
The question doesn't consider water as viscous (due to lack of coefficient of viscosity) and so you can disregard that.
