Calculating Moment of Inertia for a Soldered Wire Wheel

In summary, the problem states that a stiff uniform wire is cut, bent, and soldered to form a circular wheel with four spokes. The task is to find the moment of inertia of this wheel about an axle through its center. Using the equation for moment of inertia from the end of a rod, the solution is found to be M0L0^2/48. However, it is necessary to find the radius of the circular wheel in terms of L0 for a more accurate calculation. Assuming the wheel is a thin circular hoop, its moment of inertia can be found using the equation mr^2 when the axis of rotation is perpendicular.
  • #1
Quincy
228
0
The problem statement
A stiff uniform wire of mass M0 and length L0 is cut, bent, and the parts soldered together so that it forms a circular wheel having four identical spokes coming out from the center. None of the wire is wasted, and you can neglect the mass of the solder. What is the moment of inertia of this wheel about an axle through its center perpendicular to the plane of the wheel?


Homework Equations


I (from end of rod) = mL^2/3


The Attempt at a Solution


Itotal = 4 * ((M0/4)(L0/4)^2)/3 =

M0L0^2/48 -- What am I doing wrong?
 
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  • #2
If it forms a circular wheel, it would form a hoop with 4 rods in it. You will need to get the radius of that circle which will also be the length of a rod in terms of L0
 
  • #3
rock.freak667 said:
If it forms a circular wheel, it would form a hoop with 4 rods in it. You will need to get the radius of that circle which will also be the length of a rod in terms of L0

Should I assume that the hoop is a thin circular hoop whose moment of inertia is mr^2 when the axis of rotation is perpendicular?
 
  • #4
Quincy said:
Should I assume that the hoop is a thin circular hoop whose moment of inertia is mr^2 when the axis of rotation is perpendicular?

I think that would be fine.
 

What is "Moment of Inertia" for a wheel?

Moment of Inertia is a measure of an object's resistance to changes in its rotational motion. In the case of a wheel, it is a measure of how difficult it is to change the wheel's rotation speed.

How is "Moment of Inertia" calculated for a wheel?

The moment of inertia for a wheel can be calculated using the formula I = MR², where M is the mass of the wheel and R is the radius of the wheel.

Why is "Moment of Inertia" important for a wheel?

The moment of inertia is important for a wheel because it affects the wheel's ability to accelerate, decelerate, and maintain a constant rotation speed. A wheel with a higher moment of inertia will require more torque to change its rotation speed compared to a wheel with a lower moment of inertia.

How does the "Moment of Inertia" change for different types of wheels?

The moment of inertia can vary for different types of wheels depending on their shape and distribution of mass. For example, a solid disk will have a higher moment of inertia compared to a hollow disk with the same mass and radius.

What factors can affect the "Moment of Inertia" for a wheel?

The moment of inertia for a wheel can be affected by the wheel's mass, radius, and distribution of mass. The shape and material of the wheel can also impact the moment of inertia. For example, a wheel made of a denser material will have a higher moment of inertia compared to a wheel made of a lighter material with the same dimensions.

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