A 129-kg horizontal platform is a uniform disk of radius 1.61 m and can rotate about the vertical axis through its center. A 65.7-kg person stands on the platform at a distance of 1.07 m from the center and a 27.3-kg dog sits on the platform near the person, 1.31 m from the center. Find the moment of inertia of this system, consisting of the platform and its population, with respect to the axis.

Respuesta :

Answer:

Moment of inertia of the system is 289.088 kg.m^2

Explanation:

Given:

Mass of the platform which is a uniform disk = 129 kg

Radius of the disk rotating about vertical axis = 1.61 m

Mass of the person  standing on platform = 65.7 kg

Distance from the center of platform = 1.07 m

Mass of the dog on the platform = 27.3 kg

Distance from center of platform = 1.31 m

We have to calculate the moment of inertia.

Formula:

MOI of disk = [tex]\frac{MR^2}{2}[/tex]

Moment of inertia of the person and the dog will be mr^2.

Where m and r are different for both the bodies.

So,

Moment of inertia [tex](I_y_y )[/tex]  of the system with respect to the axis yy.

⇒ [tex]I_y_y=I_d_i_s_k + I_m_a_n+I_d_o_g[/tex]

⇒ [tex]I_y_y=\frac{M_d_i_s_k(R_d_i_s_k)^2}{2} +M_m(r_c)^2+M_d_o_g(R_c)^2[/tex]

⇒ [tex]I_y_y=\frac{129(1.61)^2}{2} +65.7(1.07)^2+27.2(1.31)^2[/tex]

⇒ [tex]I_y_y=289.088\ kg.m^2[/tex]

The moment of inertia of the system is 289.088 kg.m^2

The moment of inertia of this system is 289.088 kg. m²

First let's write the given values:

Mass of the platform which is a uniform disk = 129 kg

Radius of the disk rotating about vertical axis = 1.61 m

Mass of the person  standing on platform = 65.7 kg

Distance from the center of platform = 1.07 m

Mass of the dog on the platform = 27.3 kg

Distance from center of platform = 1.31 m

To find:

Moment of inertia=?

The moment of inertia can be calculated by using this formula:

[tex]I=\frac{M. R^2}{2}[/tex]

Therefore, moment of inertia of the person and a dog is MR² (the mass and distances differs in both cases)

Moment of inertia ([tex]I_{yy}[/tex]) of the system w.r.t. axis yy is :

[tex]I_{yy}=I_{disk}+I_{man}+I_{dog}\\[/tex]

on substituting the values in the above formula we will get:

[tex]I_{yy}=\frac{129.(1.61)^2}{2} +65.7(1.07)^2+27.2(1.31)^2\\\\I_{yy}=289.088kg.m^2[/tex]

The moment of inertia of this system is 289.088 kg. m²

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