On a fairly cool rainy day when the temperature is 20oC, the length of a steel railroad track is 20m. What will be its length on a hot a dry day when the temperature is 40oC? [coefficient of linear expansion of steel = 11 x 10-6K-1]
A. 20.013m B. 20.009m C. 20.004m D. 20.002m
Correct Answer: C
Explanation
The increase in length of the steel rail is given by = α 10 = 11 x 10-6 x 20 x (40 -20) = 11 x 10-6 x 20 x 20 = 4.4 x 10-3 ∴ Final length will be original length plus increase in length = 20 + 4.4 x 10-3 = 20 + 0.0044 = 20.0044m
