Determine the CM of a rod assuming its linear mass density λ (its mass per unit length) varies linearly from λ = λ0 at the left end to double that value, λ = 2λ0, at the right end. Determine the mass, the location of the center of mass and the moment of inertia about the CM and both ends of the rod. L =2 m and λ0=3 kg

Respuesta :

Answer:

[tex]x_c= \dfrac{5}{9}L[/tex]

[tex]I=\dfrac {7}{12}\lambda_ 0 L^3[/tex]

Explanation:

Here mass density of rod is varying so we have to use the concept of integration to find mass and location of center of mass.

At any  distance x from point A mass density

[tex]\lambda =\lambda_0+ \dfrac{2\lambda _o-\lambda _o}{L}x[/tex]

[tex]\lambda =\lambda_0+ \dfrac{\lambda _o}{L}x[/tex]

Lets take element mass at distance x

dm =λ dx

mass moment of inertia

[tex]dI=\lambda x^2dx[/tex]

So total moment of inertia

[tex]I=\int_{0}^{L}\lambda x^2dx[/tex]

By putting the values

[tex]I=\int_{0}^{L}\lambda_ ox+ \dfrac{\lambda _o}{L}x^3 dx[/tex]

By integrating above we can find that

[tex]I=\dfrac {7}{12}\lambda_ 0 L^3[/tex]

Now to find location of center mass

[tex]x_c = \dfrac{\int xdm}{dm}[/tex]

[tex]x_c = \dfrac{\int_{0}^{L} \lambda_ 0(1+\dfrac{x}{L})xdx}{\int_{0}^{L} \lambda_0(1+\dfrac{x}{L})}[/tex]

Now by integrating the above

[tex]x_c=\dfrac{\dfrac{L^2}{2}+\dfrac{L^3}{3L}}{L+\dfrac{L^2}{2L}}[/tex]

[tex]x_c= \dfrac{5}{9}L[/tex]

So mass moment of inertia [tex]I=\dfrac {7}{12}\lambda_ 0 L^3[/tex] and location of center of mass  [tex]x_c= \dfrac{5}{9}L[/tex]

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