The Elastic Modulus of a Piece of Steel Rod Under

question 40

Multiple Choice

The elastic modulus of a piece of steel rod under a load of 1600 pounds, is given by the formula , L is the original, unloaded, length in inches, A is the cross-sectional area in square inches, and l is the elongation due to a load in inches. A 60 inch long steel rod is with a cross-sectional area of A = 0.35 square inches, is stretching 0.007 inches under a load of 1600 pounds. Due to changes in temperature, the elastic modulus E of the rod is changing. Find the rate of change of the elastic modulus if the elongation is currently 0.007 and is changing at a rate of 0.00029 in/s.

• A) -1,623,324 lb/in²
• B) 1,623,324 lb/in²
• C) -5,597,667,638 lb/in²
• D) -11,363 lb/in²
• E) 11,363 lb/in²

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