- #1
brinstar
- 62
- 1
Homework Statement
Attached in a picture!
Homework Equations
I = mr^2
m = (x*y)
cm = (x/2, y/2)
The Attempt at a Solution
I was able to solve Part 1 fairly fast, but Part II has drawn a blank for me overall. I was thinking of that rotational thing from Calculus where you spin a 2D figure around the axis to make a 3D shape, but I'm really just not sure. To be honest, I'm having a very difficult time even understanding the concept of moment of inertia >.< So even if I somehow guessed how to do part II right, I really don't know what I'm doing in that section.
I) mass 1 = (20 cm)(10 cm) = 200 cm^2
mass 2 = (10 cm)(20 cm) = 200 cm^2
center of mass 1 = (20 cm i, 5 cm j)
center of mass 2 = (5 cm i, 10 cm j)
Center of Mass = (summation of (mass)(coordinates) / summation of masses) = [density of object*(200*(20 i + 5 j))+(200*(5 i + 10 j)] / density of object*(200 + 200)
= (4000 i + 1000 j + 1000 i + 2000 j) / 400
= 12.5 cm i + 7.5 cm jII) total mass of object = 4 kg
I = summation of mass*r^2
= (1 kg*100 cm^2)+(3 kg*300 cm^2)
=(100 kgcm^2)+(900 kgcm^2) = 1,000 kgcm^2
Thank you for any help and have a nice day! :-)