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MotionLab
Why bridges have expansion joints and railroad tracks have small gaps — materials grow and shrink with temperature.
A steel bridge or railroad track can change length noticeably between a cold winter night and a hot summer day — expansion joints and small gaps are engineered in specifically to absorb this movement without buckling or cracking the structure.
The expansion coefficient (α) varies significantly by material — this is why bimetallic strips (two different metals bonded together) bend predictably with temperature, a mechanism used in old-style thermostats and circuit breakers.
Length change (m)
0.004
ΔL = L · α · ΔT
What you entered
ΔL = L × α × ΔT
10 × 0.000012 × 30= 0.0036 (length units)Result
Length change (m): 0.004
A 10m length heated by 30°C expands by 0.004m.