The moment of inertia of a uniform-density disk rotating about an axle through its center can be shown to be . This result is obtained by using integral calculus to add up the contributions of all the atoms in the disk. The factor of 1/2 reflects the fact that some of the atoms are near the center and some are far from the center; the factor of 1/2 is an average of the square distances. A uniform-density disk whose mass is 16 kg and radius is 0.19 m makes one complete rotation every 0.2 s. (a) What is the moment of inertia of this disk? Entry field with correct answer 0.2888 kg · m2 (b) What is its rotational kinetic energy? Entry field with correct answer 142.52 J (c) What is the magnitude of its rotational angular momentum? Entry field with incorrect answer now contains modified data kg · m2/s

Respuesta :

(a) [tex]0.2888 kg m^2[/tex]

The moment of inertia of a uniform-density disk is given by

[tex]I=\frac{1}{2}MR^2[/tex]

where

M is the mass of the disk

R is its radius

In this problem,

M = 16 kg is the mass of the disk

R = 0.19 m is the radius

Substituting into the equation, we find

[tex]I=\frac{1}{2}(16 kg)(0.19 m)^2=0.2888 kg m^2[/tex]

(b) 142.5 J

The rotational kinetic energy of the disk is given by

[tex]K=\frac{1}{2}I\omega^2[/tex]

where

I is the moment of inertia

[tex]\omega[/tex] is the angular velocity

We know that the disk makes one complete rotation in T=0.2 s (so, this is the period). Therefore, its angular velocity is

[tex]\omega=\frac{2\pi}{T}=\frac{2\pi}{0.2 s}=31.4 rad/s[/tex]

And so, the rotational kinetic energy is

[tex]K=\frac{1}{2}(0.2888 kg m^2)(31.4 rad/s)^2=142.5 J[/tex]

(c) [tex]9.07 kg m^2 /s[/tex]

The rotational angular momentum of the disk is given by

[tex]L=I\omega[/tex]

where

I is the moment of inertia

[tex]\omega[/tex] is the angular velocity

Substituting the values found in the previous parts of the problem, we find

[tex]L=(0.2888 kg m^2)(31.4 rad/s)=9.07 kg m^2 /s[/tex]

The moment of inertia of the disk is equal to [tex]0.2888kgm^2[/tex]. The rotational kinetic energy is [tex]142.5 J[/tex] and the rotational angular momentum is [tex]9.07kgm^2/s[/tex].

How can we arrive at these results?

  • First, we will calculate the moment of inertia of the disk. This will be done with the following equation:

[tex]I=\frac{1}{2} MR^2[/tex]

In this equation, the "M" will be the mass of the disk, while the "R" will be the radius. Therefore, we can calculate the equation as follows:

[tex]I=\frac{1}{2} 16*(0.19)^2 = 0.2888kgm^2[/tex]

  • Then we can calculate the rotational kinetic energy. For this we will use the equation:

[tex]K=\frac{1}{2} IW^2[/tex]

In this equation, the "I" is the moment of inertia, while the "W" is the angular velocity.

To calculate the angular velocity, we will use the equation:

[tex]W= \frac{2\pi }{t}\\W=\frac{2\pi }{0.2} = 31.4rad/s[/tex]

Now, we can calculate rotational kinetic energy as follows:

[tex]K=\frac{1}{2} 0.2888*(31.4)^2=142.5J[/tex]

  • Now we can calculate the rotational angular momentum. This will be done through the equation:

[tex]L=IW\\L=0.2888*31.4=9.07kgm^2/s[/tex]

More information about inertia is in the link:

https://brainly.com/question/3268780