Moment of Inertia question (dead simple)

[heyall]

Homework Statement

A thin disk is 100g.
It's diameter is 20cm.
It's thickness is 2cm.

Rotation is about the central axis (ie. perpendicular to the symmetrical plane).
Answer in kg*m²

Homework Equations

I=(1/2)MR²
M is the mass
R is the radius
I is the moment of inertia

The Attempt at a Solution

R = half the diameter ∴ R = 10cm

I= (.5)(.1)(.1)²
I= 0.0005 = 5*10^^-4


I don't think the thickness matters as long as it is symmetrical all around.

The reason I ask is because this question is a multiple choice question for marks, but the answer I found (0.0005) wasn't listed as one of the options. Thanks!

 

[SammyS]

Homework Statement

A thin disk is 100g.
It's diameter is 20cm.
It's thickness is 2cm.

Rotation is about the central axis (ie. perpendicular to the symmetrical plane).
Answer in kg*m²

Homework Equations

I=(1/2)MR²
M is the mass
R is the radius
I is the moment of inertia

The Attempt at a Solution

R = half the diameter ∴ R = 10cm

I= (.5)(.1)(.1)²
I= 0.0005 = 5*10^^-4

I don't think the thickness matters as long as it is symmetrical all around.

The reason I ask is because this question is a multiple choice question for marks, but the answer I found (0.0005) wasn't listed as one of the options. Thanks!

What are the possible options?

 

[heyall]

5E-6
1E-7
5E5
2E-5
1E4

Where the letter E indicates scientific notation.

 

[haruspex]

5E-6
1E-7
5E5
2E-5
1E4

Where the letter E indicates scientific notation.

I agree, it's 5E-4.