Q. A precise steel tape measure has been calibrated at 20 degree celcius.At 40 degree C will t read high or low??? Wot will be % error??? alpha of steel=1.2*10 raise -5.

Since the length of the scale increases it will read low because anything measured using it will appear to be smaller according to the scale.

Let the length of the steel tape at 0oC be Lo

L20 = Lo(1 + 20α) = Lo(1+20×1.2×10-5)

L40 = Lo(1 + 40α) = Lo(1+40×1.2×10-5)

∆L = L40 – L20

=> ∆L = Lo (4.8×10-4)

=> ∆L/Lo = (4.8×10-4)

=>(∆L/Lo)% =4.8×10-4×100 = 0.048%

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