7. The temperature of a right rectangular prism of carbon steel with dimensions

70 × 130 x 10 mm is increased by 45 °C. The coefficient of linear expansion is 14 × 10^-6/°C.
Calculate the change in volume in mm

1 answer

To determine the change in volume of the right rectangular prism due to the change in temperature, we will use the formula for volumetric expansion, which is given by:

\[ \Delta V = V_0 \cdot \beta \cdot \Delta T \]

Where:

  • \( \Delta V \) is the change in volume,
  • \( V_0 \) is the original volume,
  • \( \beta \) is the coefficient of volumetric expansion,
  • \( \Delta T \) is the change in temperature.

The coefficient of volumetric expansion (\( \beta \)) for isotropic materials can be approximated as:

\[ \beta = 3 \cdot \alpha \]

Where \( \alpha \) is the coefficient of linear expansion.

Given:

  • \( \alpha = 14 \times 10^{-6} , \text{°C}^{-1} \)
  • \( \Delta T = 45 , \text{°C} \)

We can calculate \( \beta \):

\[ \beta = 3 \cdot (14 \times 10^{-6} , \text{°C}^{-1}) = 42 \times 10^{-6} , \text{°C}^{-1} \]

Next, we need to calculate the original volume \( V_0 \) of the prism:

\[ V_0 = \text{length} \times \text{width} \times \text{height} = 70 , \text{mm} \times 130 , \text{mm} \times 10 , \text{mm} \]

Calculating this:

\[ V_0 = 70 \times 130 \times 10 = 91000 , \text{mm}^3 \]

Now we can use the original volume, volumetric expansion coefficient, and change in temperature to find \( \Delta V \):

\[ \Delta V = 91000 , \text{mm}^3 \cdot (42 \times 10^{-6} , \text{°C}^{-1}) \cdot 45 , \text{°C} \]

Calculating this step by step:

  1. Calculate the product of \( 42 \times 10^{-6} \) and \( 45 \):

\[ 42 \times 10^{-6} \cdot 45 = 1.89 \times 10^{-3} \]

  1. Now calculate \( \Delta V \):

\[ \Delta V = 91000 , \text{mm}^3 \cdot 1.89 \times 10^{-3} = 172.59 , \text{mm}^3 \]

Thus, the change in volume \( \Delta V \) is approximately:

\[ \Delta V \approx 172.6 , \text{mm}^3 \]

Final answer: The change in volume is approximately 172.6 mm³.