Steel bars, each of length 3.0 m at 28°C, are to be used for constructing a rail line. If the linear expansivity of steel is 1.0 x 10-5°C, what is the safet...

When a material is heated, it expands in length. The linear expansion ΔL of a material can be calculated using the formula: ΔL = αLΔT where α is the coefficient of linear expansion, L is the original length of the material, and ΔT is the change in temperature. In this case, we need to calculate the amount of linear expansion of the steel bars between 28°C and 40°C. The change in temperature is: ΔT = 40°C - 28°C = 12°C The original length of each bar is: L = 3.0 m = 300 cm The coefficient of linear expansion for steel is given as 1.0 x 10^-5°C. Therefore, the linear expansion of each bar is: ΔL = αLΔT = (1.0 x 10^-5 °C)^-1 (300 cm) (12°C) = 0.036 cm To ensure that the bars do not expand into each other, a safety gap must be left between them. This safety gap is equal to the amount of linear expansion of each bar. Therefore, the safety gap is: 0.036 cm = 3.6 x 10^-2cm Therefore, the correct answer is: 3.6 x 10^-2cm.