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A steel metre scale reads exactly correctly at 20 deg C. An experiment requires distances accurate to 0.055 mm over 1 m. Within what temperature range can the scale be used? (Coefficient of linear expansion of steel = 11e-6 per deg C.)

1. 12 deg C to 28 deg C
2. 18 deg C to 22 deg C
3. 15 deg C to 25 deg C
4. 10 deg C to 30 deg C

Correct answer: 15 deg C to 25 deg C

Solution

The allowed error gives dT = (0.055e-3)/(11e-6) = 5 deg C, so the usable range is 20 +- 5 = 15 deg C to 25 deg C.

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