The Steel bed of a suspension bridge is `200\ m` long at `20°C`. If the extremes of temperature to which it might be exposed are `-30°C` to `+40°C`, how much will it contract and expand? Given: `L_0 = 200\ m` `T_0 = 20°C` Known: `a = 12 times 10^(-6)\ (°C)^(-1)` Equation: `∆L = αL_0∆T` When `T = -30°C` `∆T = -30°C - 20°C = -50°C` `∆L = αL_0∆T` `∆L = (12 times 10^(-6)\ (°C)^(-1))(200\ m)(-50°C)` When `T = 40°C` `∆T = 40°C - 20°C = 20°C` `∆L = αL_0∆T` `∆L = (12 times 10^(-6)\ (°C)^(-1))(200\ m)(20°C)`