Homework help on Moments of inertia of system

In summary, the problem involves finding the moment of inertia of a system of four masses held in position at the corners of a rectangle by light rods. The goal is to find the moment of inertia about the x axis, y axis, and an axis through O perpendicular to the page. The equation used is I=mR^2, where m is the mass and R is the distance from the axis. The center of mass is not relevant in this problem.
  • #1
Dr_bug
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Homework Statement



Four masses are held in position at the corners of a rectangle by light rods.Find the moment of inertia of the system about the x axis.Find the moment of inertia of the system about the y axis.Find the moment of inertia of the system about an axis through O and perpendicular to the page. M1 (kg) M2 (kg) M3 (kg) M4 (kg) the picture is attached.
2.70 1.70 3.70 2.10

Homework Equations



I=mR2

The Attempt at a Solution


I wasn't really sure how to start. Should I first figure out the center of mass and then use that value to find the inertia?
 

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  • #2
The center of mass has nothing to do with this. Just multiply each mass by the square of its distance from the appropriate axis and add all the terms together.
 
  • #3


As a scientist, my response would be:

To find the moment of inertia of a system, we need to use the formula I=mR^2, where m is the mass and R is the distance from the axis of rotation to the mass. In this case, we have four masses, each with its own distance from the axis of rotation. To find the moment of inertia about the x and y axes, we can use the parallel axis theorem, which states that the moment of inertia about an axis is equal to the moment of inertia about the center of mass plus the mass of the system times the distance between the two axes squared.

To start, we can find the center of mass of the system by using the formula x_cm=(m1x1+m2x2+m3x3+m4x4)/(m1+m2+m3+m4), where x1, x2, x3, and x4 are the x-coordinates of the four masses and m1, m2, m3, and m4 are their respective masses. Similarly, we can find the y-coordinate of the center of mass using the formula y_cm=(m1y1+m2y2+m3y3+m4y4)/(m1+m2+m3+m4).

Once we have the center of mass, we can use the parallel axis theorem to find the moment of inertia about the x and y axes. For the moment of inertia about an axis through O and perpendicular to the page, we can use the formula I=mx^2+my^2, where mx and my are the moment of inertia about the x and y axes, respectively.

I hope this helps in solving the problem. Remember to always double check your calculations and units to ensure accuracy.
 

What is a moment of inertia?

A moment of inertia is a measure of an object's resistance to rotational motion around a specific axis. It is calculated by multiplying the mass of an object by the square of its distance from the axis of rotation.

How is the moment of inertia of a system calculated?

The moment of inertia of a system can be calculated by adding the individual moments of inertia of each object in the system. The formula for calculating the moment of inertia of a point mass is I = mr^2, where m is the mass and r is the distance from the axis of rotation.

What factors affect the moment of inertia of a system?

The moment of inertia of a system is affected by the mass and distribution of mass within the system. Objects with larger masses or objects that are farther from the axis of rotation will have a higher moment of inertia.

Why is the moment of inertia important in physics?

The moment of inertia is important in physics because it helps us understand how objects move and behave when subjected to forces and torques. It also helps in the design of objects such as vehicles, machines, and structures, as it allows us to predict how they will respond to rotational motion.

How can I use the moment of inertia to solve problems?

The moment of inertia can be used to solve problems involving rotational motion, such as calculating the angular acceleration or torque on an object. It can also be used to determine the stability of a system and the amount of energy required to rotate an object. By understanding the moment of inertia, we can analyze and predict the behavior of objects in various scenarios.

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