- #1
adam640
- 19
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A pendulum consists of a uniform thin rod of mass 5 kg and length 2 m to which is fixed a circular disc of mass 8 kg and radius 0.4 m. There is a pivot at one end.
(a) Find the CoM and Moment of Inertia when the disc is:
(i) half way along the rod;
(ii) at the opposite end of the rod to the pivot.
I cannot do part i. I found the moment of inertia of the rod to be
I = (1/3)ML^2
I = 1/3*5*2^2
I = 6.667 kgm^2
but I don't know how to calculate for the disc.
For part ii. I found the CoM using
M = ((5*1)+(8*2))/13
M = 1.62m from pivot
I found Inertia using:
I = (1/12)ML^2 +(1/2)MR^2+ML^2
I = 5.507 kgm^2
Have I got the correct answer for part ii? How would I calculate for part i? Also, how would I find angular velocity given angular impulse? Any help greatly appreciated.
(a) Find the CoM and Moment of Inertia when the disc is:
(i) half way along the rod;
(ii) at the opposite end of the rod to the pivot.
I cannot do part i. I found the moment of inertia of the rod to be
I = (1/3)ML^2
I = 1/3*5*2^2
I = 6.667 kgm^2
but I don't know how to calculate for the disc.
For part ii. I found the CoM using
M = ((5*1)+(8*2))/13
M = 1.62m from pivot
I found Inertia using:
I = (1/12)ML^2 +(1/2)MR^2+ML^2
I = 5.507 kgm^2
Have I got the correct answer for part ii? How would I calculate for part i? Also, how would I find angular velocity given angular impulse? Any help greatly appreciated.