# physics

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A pair of eyeglass frames are made of an epoxy plastic (coefficient of linear expansion = 1.30 10-4°C−1). At room temperature (20.0°C), the frames have circular lens holes 2.27 cm in radius. To what temperature must the frames be heated if lenses 2.28 cm in radius are to be inserted into them?

• physics -

L1= 2• π• r =2• π • 2.27•10^-2 = 0.1426 m
L2 = 2• π• R =2• π • 2.28•10^-2 = 0.1433 m
ΔL = 6.566•10^-4 m
α = (ΔL/L)/ ΔT,
ΔT=(ΔL/L)/ α = (6.566•10^-4/0.1426)/1.3•10^-4 =35.42oC
T = T(o) + ΔT =20 +35.42 = 55.42 oC

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