When a 0.15 kg mass is hung from a brass wire, it stretches by 6.9 mm. If the diameter of the wire is 0.01 cm, what is its original length? Assume that the brass wire has negligible mass. The Young's modulus of a brass is 0.91×1011Pa.

Respuesta :

Answer:

L = 3.35 m

Explanation:

given,

mass(m) = 0.15 Kg

stretch(ΔL) = 6.9 mm

diameter of wire(d) = 0.01 cm

L= ?

Young's modulus (E)= 0.91 x 10¹¹ Pa

[tex]E = \dfrac{stress}{strain}[/tex]

[tex]E = \dfrac{\dfrac{P}{A}}{\dfrac{\Delta l}{L}}[/tex]

[tex]E = \dfrac{PL}{A\Delta L}[/tex]

[tex]L = \dfrac{E A \Delta L}{mg}[/tex]

[tex]L = \dfrac{0.91 \times 10^{11} \pi (0.005)^2 \times 0.0069}{0.15 \times 9.8}[/tex]

[tex]L = \dfrac{0.91 \times 10^{11} \pi (0.005)^2 \times 10^{-4}\times 0.0069}{0.15 \times 9.8}[/tex]

L = 3.35 m