When a body of mass 0.25 kg is attached to a vertical massless spring, it is extended 5.0 cm from its unstretched length of 4.0 cm. The body and spring are placed on a horizontal frictionless surface and rotated about the held end of the spring at 2.0 rev/s. How far is the spring stretched?

Respuesta :

Answer:

[tex]d=0.165m[/tex]

Explanation:

Given

[tex]m=0.25kg[/tex],[tex]x_{1}=5cm*\frac{1m}{100cm}=0.05m[/tex],[tex]x_{2}=4cm*\frac{1m}{100cm}=0.04m[/tex],[tex]v=2\frac{rev}{s}[/tex]

The tension of the spring is

[tex]F_{k}=K*x_{1}=m*g[/tex]

[tex]K=\frac{m*g}{x_{1}}[/tex]

[tex]K=\frac{0.25kg*9.8m/s^2}{0.05m}=49N/m[/tex]

The force in the spring is equal to centripetal force so

[tex]F_{c}=\frac{m*v^2}{r}[/tex]

[tex]v=w*r=2\pi*r[/tex]

But Fc is also

Fc=KxΔr

[tex]F_{c}=K*(r-x_{2})[/tex]

Replacing

[tex]m*4\pi^2*r=K*(r-x_{2})[/tex]

[tex]0.25kg*4\pi^2*r=49*(r-0.04m)[/tex]

[tex]r=0.205m[/tex]

total distance is

[tex]d=0.205-0.04=0.165m[/tex]