Understanding the Concept of Center of Mass

Oct 13, 2025 by wbrum.org 78 views

Introduction

In this problem, we are given a uniform meter rule with a body of mass 58 g suspended at the 20 cm mark. The meter rule is adjusted on a pivot until it balances horizontally at the 40 cm mark. Our goal is to determine the mass of the meter rule.

Understanding the Concept of Center of Mass

To solve this problem, we need to understand the concept of center of mass. The center of mass is the point where the entire mass of an object can be considered to be concentrated. For a uniform meter rule, the center of mass is at its midpoint, which is 50 cm from one end.

Analyzing the Situation

When the body of mass 58 g is suspended at the 20 cm mark, the meter rule is adjusted on a pivot until it balances horizontally at the 40 cm mark. This means that the weight of the body of mass 58 g is balanced by the weight of the meter rule.

Applying the Concept of Torque

To determine the mass of the meter rule, we can apply the concept of torque. Torque is a measure of the rotational force that causes an object to rotate. In this case, the torque caused by the weight of the body of mass 58 g is balanced by the torque caused by the weight of the meter rule.

Calculating the Mass of the Meter Rule

Let's denote the mass of the meter rule as m. Since the meter rule is uniform, its center of mass is at its midpoint, which is 50 cm from one end. The weight of the body of mass 58 g is balanced by the weight of the meter rule, which is given by:

W = m * g

where W is the weight of the body of mass 58 g, m is the mass of the meter rule, and g is the acceleration due to gravity.

The torque caused by the weight of the body of mass 58 g is given by:

τ = W * d

where τ is the torque, W is the weight of the body of mass 58 g, and d is the distance from the pivot to the point where the body of mass 58 g is suspended.

The torque caused by the weight of the meter rule is given by:

τ = m * g * L

where τ is the torque, m is the mass of the meter rule, g is the acceleration due to gravity, and L is the length of the meter rule.

Since the torque caused by the weight of the body of mass 58 g is balanced by the torque caused by the weight of the meter rule, we can set up the following equation:

W * d = m * g * L

Substituting the values, we get:

58 g * 0.2 m = m * 9.8 m/s^2 * 0.1 m

Simplifying the equation, we get:

11.6 g = 0.98 m

Solving for m, we get:

m = 11.85 g

Conclusion

In this problem, we determined the mass of the meter rule by applying the concept of torque and center of mass. We found that the mass of the meter rule is approximately 11.85 g.

Discussion

This problem is a classic example of how to apply the concept of torque and center of mass to solve a problem in physics. The key to solving this problem is to understand the concept of torque and how it relates to the weight of an object.

Limitations

One limitation of this problem is that it assumes that the meter rule is uniform and that its center of mass is at its midpoint. In reality, the meter rule may not be perfectly uniform, and its center of mass may not be exactly at its midpoint.

Future Work

In the future, we can extend this problem to include more complex scenarios, such as a non-uniform meter rule or a meter rule with a non-uniform distribution of mass.

References

[1] Halliday, D., Resnick, R., & Walker, J. (2013). Fundamentals of physics. John Wiley & Sons.
[2] Serway, R. A., & Jewett, J. W. (2018). Physics for scientists and engineers. Cengage Learning.

Appendix

The following is a list of formulas and equations used in this problem:

W = m * g
τ = W * d
τ = m * g * L
W * d = m * g * L

Q&A

Q: What is the concept of center of mass?

A: The center of mass is the point where the entire mass of an object can be considered to be concentrated. For a uniform meter rule, the center of mass is at its midpoint, which is 50 cm from one end.

Q: How does the concept of torque relate to the weight of an object?

A: Torque is a measure of the rotational force that causes an object to rotate. In this case, the torque caused by the weight of the body of mass 58 g is balanced by the torque caused by the weight of the meter rule.

Q: What is the formula for calculating the torque caused by the weight of an object?

A: The formula for calculating the torque caused by the weight of an object is:

τ = W * d

where τ is the torque, W is the weight of the object, and d is the distance from the pivot to the point where the object is suspended.

Q: What is the formula for calculating the torque caused by the weight of the meter rule?

A: The formula for calculating the torque caused by the weight of the meter rule is:

τ = m * g * L

where τ is the torque, m is the mass of the meter rule, g is the acceleration due to gravity, and L is the length of the meter rule.

Q: How do we determine the mass of the meter rule?

A: We determine the mass of the meter rule by setting up an equation based on the concept of torque and center of mass. The equation is:

W * d = m * g * L

Substituting the values, we get:

58 g * 0.2 m = m * 9.8 m/s^2 * 0.1 m

Simplifying the equation, we get:

11.6 g = 0.98 m

Solving for m, we get:

m = 11.85 g

Q: What are some limitations of this problem?

A: One limitation of this problem is that it assumes that the meter rule is uniform and that its center of mass is at its midpoint. In reality, the meter rule may not be perfectly uniform, and its center of mass may not be exactly at its midpoint.

Q: What are some future directions for this problem?

A: In the future, we can extend this problem to include more complex scenarios, such as a non-uniform meter rule or a meter rule with a non-uniform distribution of mass.

Q: What are some references for further reading?

A: Some references for further reading include:

[1] Halliday, D., Resnick, R., & Walker, J. (2013). Fundamentals of physics. John Wiley & Sons.
[2] Serway, R. A., & Jewett, J. W. (2018). Physics for scientists and engineers. Cengage Learning.

Q: What is the appendix?

A: The appendix is a list of formulas and equations used in this problem. These formulas and equations are used to derive the equation 11.6 g = 0.98 m, which is used to solve for the mass of the meter rule.

Appendix

The following is a list of formulas and equations used in this problem:

W = m * g
τ = W * d
τ = m * g * L
W * d = m * g * L

These formulas and equations are used to derive the equation 11.6 g = 0.98 m, which is used to solve for the mass of the meter rule.