Moment of Inertia of Rod About Axis XX': ML2/3sin2α

AI Thread Summary
The moment of inertia of a rod about an axis XX' through its center of mass at an angle α is given by the formula ML²/3sin²α. The discussion highlights confusion regarding the appearance of the sin² term in the equation. It emphasizes that the distance along the axis does not influence moments about the axis; instead, the relevant distance is from the XX' axis to points on the rod. A suggestion is made to set up an integral to better understand the calculation. Understanding these concepts is crucial for accurately determining the moment of inertia in this scenario.
Aditya1998
Messages
1
Reaction score
0
1. The problem statementα, all variables and given/known data

The moment of inertia of a Rod over an
Axis XX' passing through the center of mass of the Rod at an angle α is-

Homework Equations


Moment of Inertia of Rod about the end, I =ML2/3

The Attempt at a Solution


I=ML2/3
Answer of the question is ML2/3sin2α

I didn't understood how sin2 came because even if we shift OL over the axis XX' then

OX=OLcosα

[/B]
 

Attachments

  • _20151121_160521.JPG
    _20151121_160521.JPG
    11.3 KB · Views: 418
Physics news on Phys.org
Hint: Set up an integral.
 
Aditya1998 said:
I didn't understood how sin2 came because even if we shift OL over the axis XX' then
OX=OLcosα
The distance along the axis, OX, does not affect moments about the axis. The distance of interest is from the XX' axis to the points on the rod.
 
Kindly see the attached pdf. My attempt to solve it, is in it. I'm wondering if my solution is right. My idea is this: At any point of time, the ball may be assumed to be at an incline which is at an angle of θ(kindly see both the pics in the pdf file). The value of θ will continuously change and so will the value of friction. I'm not able to figure out, why my solution is wrong, if it is wrong .
TL;DR Summary: I came across this question from a Sri Lankan A-level textbook. Question - An ice cube with a length of 10 cm is immersed in water at 0 °C. An observer observes the ice cube from the water, and it seems to be 7.75 cm long. If the refractive index of water is 4/3, find the height of the ice cube immersed in the water. I could not understand how the apparent height of the ice cube in the water depends on the height of the ice cube immersed in the water. Does anyone have an...
Back
Top