/*! This file is auto-generated */ .wp-block-button__link{color:#fff;background-color:#32373c;border-radius:9999px;box-shadow:none;text-decoration:none;padding:calc(.667em + 2px) calc(1.333em + 2px);font-size:1.125em}.wp-block-file__button{background:#32373c;color:#fff;text-decoration:none} Problem 46 The density of a \(1.00-\mathrm{... [FREE SOLUTION] | 91Ó°ÊÓ

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The density of a \(1.00-\mathrm{m}\) long rod can be described by the linear density function \(\lambda(x)=\) \(100 \cdot \mathrm{g} / \mathrm{m}+10.0 x \mathrm{~g} / \mathrm{m}^{2}\) One end of the rod is positioned at \(x=0\) and the other at \(x=1.00 \mathrm{~m} .\) Determine (a) the total mass of the rod, and (b) the center-of-mass coordinate.

Short Answer

Expert verified
Answer: (a) The total mass of the rod is 105 g. (b) The center-of-mass coordinate is approximately 0.54 m.

Step by step solution

01

Find the total mass of the rod m

To find the total mass of the rod, we must integrate the linear density function λ(x) over the length of the rod, from x=0 to x=1 m. The total mass m can be calculated by integrating the function: $$m = \int_{0}^{1} \lambda(x)dx$$ Now, plug in the given linear density function λ(x) = 100g/m + 10.0x(g/m²): $$m = \int_{0}^{1} (100 + 10x)dx$$
02

Evaluate the integral for the mass

Integrate the function with respect to x: $$m = \left[100x + \frac{10x^2}{2}\right]_{0}^{1}$$ Evaluate the integral at the limits: $$m = (100(1) + \frac{10(1)^2}{2}) - (100(0) + \frac{10(0)^2}{2})$$ $$m = 100 + 5 = 105 \mathrm{~g}$$ The total mass of the rod is 105 g.
03

Find the center-of-mass coordinate x_cm

To find the one-dimensional center-of-mass coordinate x_cm, we can use the formula: $$x_{\mathrm{cm}} = \frac{1}{m} \int_{0}^{1} x\lambda(x) dx$$ Plug in the given linear density function λ(x) = 100g/m + 10.0x(g/m²), and the total mass m = 105g: $$x_{\mathrm{cm}} = \frac{1}{105} \int_{0}^{1} x(100 + 10x) dx$$
04

Evaluate the integral for x_cm

Expand the integrand and integrate the function with respect to x: $$x_{\mathrm{cm}} = \frac{1}{105} \int_{0}^{1} (100x + 10x^2) dx$$ $$x_{\mathrm{cm}} = \frac{1}{105} \left[\frac{100x^2}{2} + \frac{10x^3}{3}\right]_{0}^{1}$$ Evaluate the integral at the limits: $$x_{\mathrm{cm}} = \frac{1}{105}\left(\frac{100(1)^2}{2} + \frac{10(1)^3}{3}\right) - \frac{1}{105}\left(\frac{100(0)^2}{2} + \frac{10(0)^3}{3}\right)$$ $$x_{\mathrm{cm}} = \frac{1}{105}(50 + \frac{10}{3})$$ Now, simplify the expression for x_cm: $$x_{\mathrm{cm}} \approx \frac{1}{105}(56.67) \approx 0.54 \mathrm{~m}$$ The center-of-mass coordinate is approximately 0.54 m. So the results are: (a) The total mass of the rod is 105 g. (b) The center-of-mass coordinate is approximately 0.54 m.

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Linear Density Function
Understanding the concept of a linear density function is crucial in calculating varying densities along an object. A linear density function tells us how the mass is distributed along a specific length of a material or object. In our specific exercise, the linear density function is given as \[ \lambda(x) = 100\, \text{g/m} + 10.0x\, \text{g/m}^2 \]This implies that the density starts at 100 g/m and increases by 10 g/m² for each additional meter along the rod. Consequently, as you move along the rod from one end to the other, the density isn't constant—it increases linearly with distance.
Understanding how mass distribution varies can be essential in many real-world applications, such as engineering and material fabrication.
Integration in Physics
Integration in physics is a mathematical technique often used to find quantities when dealing with continuous distributions or changes. In the case of our rod, we need to integrate to find the total mass because the density isn't uniform—it changes along the rod. The integration of the linear density function over the specified length of the rod enables us to calculate the total mass:\[ m = \int_{0}^{1} \lambda(x)\, dx = \int_{0}^{1} (100 + 10x)\, dx \]Integration helps by adding up the infinitely small pieces of mass along the rod, taking into account the changing density.
This technique is not only applicable to mass calculations but also to other areas in physics, such as finding electric charge, gravitational force, and fields, among others.
Mass Calculation
To determine the total mass of the rod, we integrate the linear density function along the length of the rod. The process of integration involves finding the antiderivative of the linear density function and then evaluating it over the limits of the rod:\[ m = \left[ 100x + \frac{10x^2}{2} \right]_{0}^{1} = 100 + 5 = 105 \text{ g} \]This calculation shows that the total mass is 105 g. It's important to follow each step, as integration accumulates small changes in density over the entire length. Once the integration results are evaluated at specific boundaries, you can obtain a concrete value representing the full mass, essential in many physical computations.
Physics Problem Solving
Physics problem-solving often requires a step-by-step approach to translate a problem statement into calculations. In this exercise, solving for the center of mass requires understanding the distribution of mass and performing integration. First, ensure you understand the problem and what each function and formula represents.
  • Identify the need for integration when dealing with variable densities or quantities.
  • Calculate intermediate values like total mass before approaching complex concepts like the center of mass.
  • Use known formulas like the center of mass formula, integrating within appropriate limits to find desired parameters.
Finally, translating these steps into the computation reveals that sometimes breaking complex problems into smaller parts helps manage and solve them efficiently.
In this case, systematically integrating and interpreting each outcome was key to finding both the total mass and the center of mass successfully.

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Most popular questions from this chapter

You are piloting a spacecraft whose total mass is \(1000 \mathrm{~kg}\) and attempting to dock with a space station in deep space. Assume for simplicity that the station is stationary, that your spacecraft is moving at \(1.0 \mathrm{~m} / \mathrm{s}\) toward the station, and that both are perfectly aligned for docking. Your spacecraft has a small retro-rocket at its front end to slow its approach, which can burn fuel at a rate of \(1.0 \mathrm{~kg} / \mathrm{s}\) and with an exhaust velocity of \(100 \mathrm{~m} / \mathrm{s}\) relative to the rocket. Assume that your spacecraft has only \(20 \mathrm{~kg}\) of fuel left and sufficient distance for docking. a) What is the initial thrust exerted on your spacecraft by the retro-rocket? What is the thrust's direction? b) For safety in docking, NASA allows a maximum docking speed of \(0.02 \mathrm{~m} / \mathrm{s}\). Assuming you fire the retro-rocket from time \(t=0\) in one sustained burst, how much fuel (in kilograms) has to be burned to slow your spacecraft to this speed relative to the space station? c) How long should you sustain the firing of the retrorocket? d) If the space station's mass is \(500,000 \mathrm{~kg}\) (close to the value for the ISS), what is the final velocity of the station after the docking of your spacecraft, which arrives with a speed of \(0.02 \mathrm{~m} / \mathrm{s}\) ?

A uniform chain with a mass of \(1.32 \mathrm{~kg}\) per meter of length is coiled on a table. One end is pulled upward at a constant rate of \(0.47 \mathrm{~m} / \mathrm{s}\). a) Calculate the net force acting on the chain. b) At the instant when \(0.15 \mathrm{~m}\) of the chain has been lifted off the table, how much force must be applied to the end being raised?

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The distance between a carbon atom \((m=12 \mathrm{u})\) and an oxygen atom \((m=16 \mathrm{u})\) in a carbon monoxide \((\mathrm{CO})\) molecule is \(1.13 \cdot 10^{-10} \mathrm{~m} .\) How far from the carbon atom is the center of mass of the molecule? \((1 \mathrm{u}=1\) atomic mass unit. \()\)

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