How Do You Calculate the Moment of Inertia for a Tapered Tube?

In summary, the conversation is about calculating the moment of inertia of a cantilevered tapered tube with mid-thickness large and small radii. The equations used include the area of the larger and smaller ends of the tube, as well as the area at a distance x. The difference between calculating the second moment of area and the mass moment of inertia is discussed, with a preference for the second moment of area. The question of how to calculate the second moment of area for a circle is also raised.
  • #1
Sud89
5
0

Homework Statement


To calculate the moment of inertia of a cantilevered tapered tube with mid-thickness large radius RL and mid-thickness small radius RS

Homework Equations


upload_2015-11-9_19-52-48.png


The Attempt at a Solution


Area of the larger end of the tube
AL=2*pi*RL*t
Area of the smaller end of the tube
AS=2*pi*RS*t
Area of the tube at a distance x is
AX=2*pi*RX*t
RX=RL - x*tanalpha
tanalpha=deltaR/L
deltaR = RL-RS[/B]
 

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  • #2
When you say 'calculate the moment of inertia', do you mean calculate the 'second moment of area' of the cross section of the tube (units of L4 ) or do you mean calculate the 'mass moment of inertia' of this piece (units of ML2 )? It makes a difference ...
 
  • #3
SteamKing said:
When you say 'calculate the moment of inertia', do you mean calculate the 'second moment of area' of the cross section of the tube (units of L4 ) or do you mean calculate the 'mass moment of inertia' of this piece (units of ML2 )? It makes a difference ...

Second moment of area
 
  • #4
Sud89 said:
Second moment of area
How would you calculate the second moment of area for a circle?
 

1. What is the moment of inertia formula?

The moment of inertia formula is a mathematical expression that calculates the rotational inertia of an object. It is represented by the symbol "I" and is defined as the sum of the products of each particle's mass and the square of its distance from the axis of rotation.

2. How is moment of inertia different from mass?

Mass measures the amount of matter in an object, while moment of inertia measures the distribution of mass around an axis of rotation. This means that two objects with the same mass can have different moments of inertia if their mass is distributed differently.

3. What are the units of the moment of inertia formula?

The units of the moment of inertia formula depend on the units used for mass and distance. In the SI system, the units are typically kg·m², while in the US customary system, the units are typically sl·ft². However, it is important to use consistent units for both mass and distance in the formula.

4. How is the moment of inertia formula used in real life?

The moment of inertia formula is used in many real-life applications, such as engineering, physics, and sports. It helps engineers design structures and machines that can withstand rotational forces, and it is used in calculations for objects in motion, such as spinning tops or rotating planets. In sports, it is used to analyze the performance of athletes, such as figure skaters or gymnasts.

5. Can the moment of inertia formula be derived?

Yes, the moment of inertia formula can be derived using calculus and the principle of rotational inertia. It involves breaking down an object into infinitesimal particles, calculating the moment of inertia of each particle, and then integrating them to find the total moment of inertia. However, the formula is often given as a known equation in physics and engineering problems rather than being derived each time.

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