Metal rods of length 20m each are laid end to end to form a bridge at 25oC. What gap will be provided between consecutive rails for the bridge to withstand 75oC?
[Linear expansivity of the material = 2.0 x 10-5K-1
A
0.20m
B
0.22m
C
0.25m
D
0.02m
Verified Correct Answer: D.
Physical Principles & Numerical Solution
Safety gap = expansion of the rod
= \(\alpha \times L_0 \times \Delta t\)
where \(\alpha\) = linear expansivity of the material
\(L_0\) = Initial length of the material
\(\Delta t\) = Change in temperature
\(\therefore\) The safety gap = \(2 \times 10^{-5} \times 20 \times (75 - 25)\)
= \(2 \times 10^{-5} \times 10^3\)
= \(2 \times 10^{-2} m\)
= 0.02 m
Source: Myschool Past Questions Archive (Record #12943)