When a piece of wood is suspended from the hook of a spring balance, it reads 70 gf. The wood is now lowered into water.What reading do you expect on the scale of spring balance?

Answer

To solve the problem, we need to understand the concept of buoyancy and Archimedes' principle. When an object is submerged in a fluid, it experiences an upward force called buoyant force, which reduces the effective weight of the object in the fluid.

### Step-by-Step Solution:

1. **Identify the Weight of the Wood in Air**:
The wood weighs 70 gf (gram-force) when suspended in air. This is the force due to gravity acting on the wood.

2. **Understand the Concept of Buoyant Force**:
When the wood is submerged in water, it will experience an upward buoyant force. According to Archimedes' principle, the buoyant force is equal to the weight of the fluid displaced by the submerged part of the object.

3. **Determine the Buoyant Force**:
The buoyant force acting on the wood will reduce the effective weight of the wood when it is submerged in water. The amount of buoyant force depends on the volume of the wood and the density of water.

4. **Calculate the New Reading on the Spring Balance**:
Since the wood is floating, the reading on the spring balance will be equal to the weight of the wood minus the buoyant force. However, since we do not have the specific volume or density of the wood, we can conclude that the reading will be less than 70 gf.

5. **Conclusion**:
The reading on the spring balance when the wood is submerged in water will be less than 70 gf. The exact value cannot be determined without additional information about the wood's volume and density.

### Expected Reading:
The reading on the spring balance when the wood is submerged in water will be less than 70 gf.