AP Calculus AB: 10.9.1 Center of Mass
This content explains the concept of the center of mass in a system of point masses, detailing how to calculate it using moments about the x- and y-axes. It includes definitions, formulas, and example problems to illustrate the calculation of total moments and the resulting center of mass.
Center of Mass
The center of mass of an object is the point where you can assume all the mass is concentrated.
• A moment can be thought of as a system’s tendency to rotate about an axis.
• The moment about the y-axis is .The moment about the x-axis is .
The center of mass, , can be found by dividing the moments by the total mass:
Key Terms
Center of Mass
The center of mass of an object is the point where you can assume all the mass is concentrated.
• A moment can be thought of as a system...
note
The center of mass is the point where you can assume all the mass is concentrated. If you support an object at the center of mass, the obje...
Masses of 2 lb, 4 lb and 1 lb are located in a plane at points (3, 1), (0, 0), and (1, 4), respectively. What is the center of mass of the system?
(1, 6/7)
Suppose that m1, m2, …, mn is a collection of point masses situated in a plane at (x1, y1 ), (x2, y2 ), …, (xn, yn ), respectively. What are the total moments with respect to the x- and y-axes?
My=n∑k=1xkmk, Mx=n∑k=1ykmk
Masses of 2 lb, 4 lb and 1 lb are located in a plane at points (3, 1), (0, 0), and (1, 4), respectively. Which of the following is the total moment with respect to the y‑axis?
M y = 7
Masses of 2 lb, 4 lb and 1 lb are located in a plane at points (3, 1), (0, 0), and (1, 4), respectively. Which of the following is the total moment with respect to the x‑axis?
M x = 6
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| Term | Definition |
|---|---|
Center of Mass |
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note |
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Masses of 2 lb, 4 lb and 1 lb are located in a plane at points (3, 1), (0, 0), and (1, 4), respectively. What is the center of mass of the system? | (1, 6/7) |
Suppose that m1, m2, …, mn is a collection of point masses situated in a plane at (x1, y1 ), (x2, y2 ), …, (xn, yn ), respectively. What are the total moments with respect to the x- and y-axes? | My=n∑k=1xkmk, Mx=n∑k=1ykmk |
Masses of 2 lb, 4 lb and 1 lb are located in a plane at points (3, 1), (0, 0), and (1, 4), respectively. Which of the following is the total moment with respect to the y‑axis? | M y = 7 |
Masses of 2 lb, 4 lb and 1 lb are located in a plane at points (3, 1), (0, 0), and (1, 4), respectively. Which of the following is the total moment with respect to the x‑axis? | M x = 6 |
Which of the following does not accurately complete the sentence? The center of mass of an object is _____________. | the geometric center of the object |
Suppose that m1, m2, …, mn is a collection of point masses situated in a plane at (x1, y1 ), (x2, y2 ), …, (xn, yn ), respectively. What are the coordinates of the center of mass of the system? | X=n∑k=1xkmkn∑k=1mk, Y=n∑k=1ykmkn∑k=1mk |
Masses of 2 lb, 6 lb, 2 lb and 10 lb are located in a plane at points (0, 2), (3, 4), (0, 1), and (1, 1), respectively. Which of the following is the center of mass of the entire system? | (7/5, 2) |