As shown in the figure, in an experiment to determine Young's modulus of a wire, the extension-load curve is a straight line through the origin making 45° with the load axis. The length of wire is 62.8 cm and its diameter is 4 mm. Young's modulus is x × 10⁴ N m⁻². The value of x is:

Question

G1 Physics · Accepted Answer

From the 45° graph, ΔL/F = 1 in the plotted units, so F = ΔL numerically. Young's modulus Y = FL/(AΔL) = L/A. With L = 62.8 × 10⁻² m and radius = 2 × 10⁻³ m, Y = 0.628/[π(2×10⁻³)²] ≈ 5 × 10⁴ N m⁻². Hence x = 5.