To allow for expansion in the summer when temperatures rise, a steel railway line laid in cold weather is pre-stressed by applying a force of 2.6 × 10⁵ N to the rail of cross-sectional area 5.0 × 10⁻³ m².
If the railway line is not pre-stressed, a strain of 1.4 × 10⁻⁵ is caused by each degree Celsius rise in temperature. The Young modulus of the steel is 2.1 × 10¹¹ Pa.
a. State and explain whether the force applied to the rail when it is laid should be tensile or compressive.
b. Calculate:
i. The strain produced when the rail is laid
ii. The temperature rise when the rail becomes unstressed.