The masses and coordinates of four particles are as follows: 26 g, x = 3.0 cm, y = 3.0 cm; 18 g, x = 0, y = 6.0 cm; 15 g, x = -4.5 cm, y = -4.5 cm; 23 g, x = -3.0 cm, y = 6.0 cm. What are the rotational inertias of this collection about the (a) x, (b) y, and (c) z axes?

Respuesta :

Answer:

1)[tex]I_{x}=2013.1gcm^{2}[/tex]

2)[tex]I_{y}=744.75gcm^{2}[/tex]

3)[tex]I_{z}=2747.85gcm^{2}[/tex]

Explanation:

Since the given masses are completely in xy plane we have

Moment of inertia about x axis equals

[tex]I_{x}={\sum y_{i}^{2}m_{i}}[/tex]

Applying the values we get

[tex]I_{x}={26\times 3^{2}+23\times 6^2+15\times (-4.5)^{2}+18\times 6^{2}}\\\\\therefore I_{x}=2013.1gcm^{2}[/tex]

Similarly

Moment of inertia about y axis equals

[tex]I_{y}={\sum x_{i}^{2}m_{i}}[/tex]

Applying the values we get

[tex]I_{x}={26\times 3^{2}+23\times (-3)^2+15\times (-4.5)^{2}+18\times 0^{2}}\\\\\therefore I_{y}=744.75gcm^{2}[/tex]

Now by theorem of perpendicular axis of moment of inertia we have

[tex]I_{z}=I_{x}+I_{y}[/tex]

Appying values we get

[tex]I_{z}=2013.1+744.75=2747.85gcm^{2}[/tex]

The rotational inertia of this collection about the x,  y, and z axes are 2013.1 g-cm², 744.75 g-cm² and 2747.85 g-cm² respectively.

What is rotational inertia?

The rotational inertia is the product of mass of the body and the square of the radius of the rotation.

it can be given as,

[tex]I=mr^2[/tex]

The masses and coordinates of four particles are as follows:

26 g,  x = 3.0 cm,   y = 3.0 cm;

8 g,   x = 0 cm,      y = 6.0 cm;

15 g,   x = -4.5 cm,  y = -4.5 cm;

23 g,  x = -3.0 cm,  y = 6.0 cm.

For all the particles, the rotational inertia about x-axis can be given as using the above formula as,

[tex]I_x=\sum m_i(y_i)^2[/tex]

Put the values as,

[tex]I_x=26(3)^2+18(6)^2+15(-4.5)+23(6)\\I_x=2013.1\rm \; g-cm^2[/tex]

The rotational inertia about x-axis can be given as using the above formula as,

[tex]I_y=\sum m_i(x_i)^2[/tex]

Put the values as,

[tex]I_y=26(3)^2+18(0)^2+15(-4.5)+23(-3)\\I_y=744.75\rm \; g-cm^2[/tex]

The rotational inertia about x-axis is the sum of rotational inertia along xy- axis. Thus,

[tex]I_z=2013.1+744.75\\I_z=2747.85\rm \; g-cm^2[/tex]

Hence, the rotational inertia of this collection about the x,  y, and z axes are 2013.1 g-cm², 744.75 g-cm² and 2747.85 g-cm² respectively.

Learn more about rotational inertia here;

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