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Patdon10
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Homework Statement
Steel rails for a train track are laid in a region subject to extremes of temperature. The distance from one juncture to the next is 5.4 m, and the cross-sectional area of the rails is 60 cm2. If the rails touch each other without buckling at the maximum temperature, 51 °C, how much space will there be between the rails at -17 °C? (The linear expansion coefficient for steel is 1.3 10-5 °C−1.)
Homework Equations
ΔL = α*L*ΔT
ΔA = 2αAΔT = 2L(αLΔT)
The Attempt at a Solution
Giving the cross-sectional area is confusing. I don't understand why you would need it? From what I understand of this problem, it is simply two "sections" of rails connected. At 51 degress, they are touching. I need to find how much they shrink at -17 degrees. It doesn't matter if it's a wire or a rail, it will shrink or lengthen accordingly (correct?)
ΔL = αLΔT
ΔL = (1.3*10^-5)(5.4m)(-17-51)
ΔL = -0.00477 m
Because two rails are shrinking I need to double that to 0.009547 m.
That's how much space I'm calculating and it's saying it's the wrong answer. Anyone know what I'm doing wrong?
Thanks in advance.