Question 8: Is there any difference in the length of 20 m steel girder when standing vertically and horizontally?
Yes, there would be a slight difference in the lengths of the girder when placed vertically and horizontally.
When the girder is placed on the ground, it is under the stress of its own weight. The stress is the force (due to its weight) per unit area. Mathematically, Stress = Force/Area.
- Now when the girder is standing in the vertical position, the weight of the girder acts vertically downward as shown in the figure. Therefore, a force is exerted on the girder in the lengthwise direction. This force produces a compressive strain = Δℓ/L in the girder. This reduces the length of the girder.
- When the girder is placed in a horizontal position, it doesn’t experience any force in the lengthwise direction. Hence, there is no strain and no decrease in the length of 20 m girder.
Therefore, the length of the girder would be a slight less when it is standing vertically than when it is placed horizontally.