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A piece of wax wieghs 18.03 g in air. A ...

A piece of wax wieghs 18.03 g in air. A piece of metal is found to weigh 17.03 g in water. It is tied to the wax and both together weigh 15.23 g in water. Then, the specific gravity of wax is

A

`18.03/17.03`

B

`17.03/18.03`

C

`18.03/19.83`

D

`15.03/19.83`

Text Solution

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The correct Answer is:
To find the specific gravity of the wax, we will follow these steps: ### Step 1: Determine the weight of the wax in air The weight of the wax in air is given as: \[ W_{\text{wax}} = 18.03 \, \text{g} \] ### Step 2: Determine the weight of the metal in water The weight of the metal in water is given as: \[ W_{\text{metal, water}} = 17.03 \, \text{g} \] ### Step 3: Determine the combined weight of the wax and metal in water When the wax and the metal are tied together, their combined weight in water is: \[ W_{\text{combined, water}} = 15.23 \, \text{g} \] ### Step 4: Calculate the buoyant force acting on the wax and metal The apparent weight in water is given by the equation: \[ W_{\text{metal}} - F_{\text{b, metal}} + W_{\text{wax}} - F_{\text{b, wax}} = W_{\text{combined, water}} \] Where: - \( F_{\text{b, metal}} \) is the buoyant force on the metal. - \( F_{\text{b, wax}} \) is the buoyant force on the wax. From the information given, we can express this as: \[ W_{\text{metal}} + W_{\text{wax}} - (F_{\text{b, metal}} + F_{\text{b, wax}}) = W_{\text{combined, water}} \] Substituting the known values: \[ 17.03 + 18.03 - (F_{\text{b, metal}} + F_{\text{b, wax}}) = 15.23 \] ### Step 5: Solve for the total buoyant force Calculating the left side: \[ 35.06 - (F_{\text{b, metal}} + F_{\text{b, wax}}) = 15.23 \] Rearranging gives: \[ F_{\text{b, metal}} + F_{\text{b, wax}} = 35.06 - 15.23 = 19.83 \, \text{g} \] ### Step 6: Relate the buoyant force to the volume of the wax The buoyant force is also given by the formula: \[ F_{\text{b}} = \rho_{\text{fluid}} \cdot V \cdot g \] Where: - \( \rho_{\text{fluid}} \) is the density of the fluid (water in this case). - \( V \) is the volume of the object submerged. - \( g \) is the acceleration due to gravity. Assuming the density of water is approximately \( 1 \, \text{g/cm}^3 \), we can express the buoyant force on the wax as: \[ F_{\text{b, wax}} = \rho_{\text{water}} \cdot V_{\text{wax}} \cdot g = V_{\text{wax}} \cdot g \] ### Step 7: Set up the equation for the density of wax From the weight of the wax: \[ W_{\text{wax}} = \rho_{\text{wax}} \cdot V_{\text{wax}} \cdot g \] Substituting the values we have: \[ 18.03 = \rho_{\text{wax}} \cdot V_{\text{wax}} \cdot g \] ### Step 8: Combine the equations to find the specific gravity We have: \[ \rho_{\text{wax}} \cdot V_{\text{wax}} \cdot g = 18.03 \] And: \[ V_{\text{wax}} \cdot g = 19.83 \] Dividing these two equations: \[ \frac{\rho_{\text{wax}} \cdot V_{\text{wax}} \cdot g}{V_{\text{wax}} \cdot g} = \frac{18.03}{19.83} \] This simplifies to: \[ \rho_{\text{wax}} = \frac{18.03}{19.83} \] ### Step 9: Calculate the specific gravity The specific gravity of the wax is defined as: \[ \text{Specific Gravity} = \frac{\rho_{\text{wax}}}{\rho_{\text{water}}} \] Since \( \rho_{\text{water}} \approx 1 \, \text{g/cm}^3 \): \[ \text{Specific Gravity} = \frac{18.03}{19.83} \] ### Final Calculation Calculating the specific gravity: \[ \text{Specific Gravity} \approx 0.909 \] ### Conclusion The specific gravity of the wax is approximately \( 0.909 \). ---
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