The reading of a spring balance when a mass is weighed on it in air is 40 gm. When the mass is immersed in water, its reading is 20 gm. The specific gravity of the mass is

Options

A. 3
B. 2
C. 1.5
D. 2.5

Answer

To solve the problem of finding the specific gravity of the mass, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Given Values:**
- Weight of the mass in air (W_air) = 40 g
- Weight of the mass in water (W_water) = 20 g

2. **Understand the Concept of Specific Gravity:**
- Specific gravity (SG) is defined as the ratio of the weight of the mass in air to the weight of the water displaced by the mass when submerged in water.

3. **Calculate the Weight of Water Displaced:**
- The weight of water displaced can be calculated using the formula:
\[ \text{Weight of Water Displaced} = W_{\text{air}} - W_{\text{water}} \]
- Substituting the values:
\[ \text{Weight of Water Displaced} = 40 \, \text{g} - 20 \, \text{g} = 20 \, \text{g} \]

4. **Calculate the Specific Gravity:**
- The formula for specific gravity is:
\[ \text{Specific Gravity} (SG) = \frac{W_{\text{air}}}{\text{Weight of Water Displaced}} \]
- Substituting the values:
\[ SG = \frac{40 \, \text{g}}{20 \, \text{g}} = 2 \]

5. **Conclusion:**
- The specific gravity of the mass is 2. This means the mass is twice as dense as water.

### Final Answer:
The specific gravity of the mass is 2.

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