/*! 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 35 (a) By what percentage does your... [FREE SOLUTION] | 91Ó°ÊÓ

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(a) By what percentage does your rest mass increase when you climb 30 \(\mathrm{m}\) to the top of a ten-story building? Are you aware of this increase? Explain. (b) By how many grams does the mass of a \(120-\mathrm{g}\) spring with force constant 200 \(\mathrm{N} / \mathrm{cm}\) change when you compress it by 6.0 \(\mathrm{cm} \%\) Does the mass increase or decrease? Would you notice the change in mass if you were holding the spring? Explain.

Short Answer

Expert verified
Both the mass increase by climbing and the mass decrease by compressing the spring are negligible and imperceptible.

Step by step solution

01

Understand the Concept of Mass-Energy Equivalence

The principle of mass-energy equivalence is given by the equation \( E = mc^2 \), where \( E \) is the energy, \( m \) is the mass, and \( c \) is the speed of light in a vacuum \( \approx 3 \times 10^8 \text{ m/s} \). This equation implies that the energy of a system contributes to its mass.
02

Calculate the Potential Energy Gained

For part (a), calculate the increase in potential energy when you climb 30 meters. The potential energy \( U \) can be calculated using \( U = mgh \), where \( m \) is the mass of the person (assume \( m = 70 \text{ kg} \)), \( g \approx 9.8 \text{ m/s}^2 \) (acceleration due to gravity), and \( h = 30 \text{ m} \). Thus, \( U = 70 \cdot 9.8 \cdot 30 \).
03

Convert the Energy to Mass

Using the computed potential energy from Step 2, convert this energy increase into an equivalent mass increase using \( \Delta m = \frac{\Delta E}{c^2} \). Substituting the values, calculate \( \Delta m \).
04

Calculate Percentage Increase in Mass

Determine the percentage increase by \( \left(\frac{\Delta m}{m}\right) \times 100\% \). Given that \( \Delta m \) is very small compared to \( m \), explain why the change is practically imperceptible.
05

Calculate the Spring's Energy

For part (b), use the spring's potential energy formula \( U = \frac{1}{2}k x^2 \), where \( k = 200 \text{ N/cm} \) (convert this to \( 20000 \text{ N/m} \)) and \( x = 6.0 \text{ cm} = 0.06 \text{ m} \). Calculate the spring's energy when compressed.
06

Convert Spring Energy to Mass Change

Convert the energy change of the spring into a mass change using \( \Delta m = \frac{\Delta E}{c^2} \), similar to Step 3.
07

Consider the Magnitude of Mass Change

Given the very small value for \( \Delta m \) calculated from the spring's energy, discuss why this decrease in mass is negligible and undetectable to human senses.
08

Summarize Findings for Both Parts

For part (a), the change in mass is negligible and undetectable because it's incredibly tiny. For part (b), the mass of the spring decreases slightly upon compression due to energy conservation, but this change is also unnoticeable.

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Key Concepts

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

Potential Energy
Potential energy is an important concept in physics, especially when dealing with gravitational fields and height changes. When you climb to the top of a building, your position in the Earth's gravitational field changes, increasing your potential energy. This increase can be calculated with the formula:- Potential energy, \( U = mgh \), where: - \( m \) is your mass (in kilograms) - \( g \) is the acceleration due to gravity (approximately \( 9.8 \, \text{m/s}^2 \)) - \( h \) is the height climbed (in meters)So, if you weigh 70 kg and climb 30 meters, you gain a certain amount of potential energy. This energy gain is a small fraction of the energy needed to affect or perceive a change in mass. Hence, any increase in your relativistic mass is negligible and unnoticeable because it involves an incredibly tiny value.
Energy Conservation
The law of energy conservation is a fundamental principle in physics. It states that energy cannot be created or destroyed, only transformed from one form to another. When you climb a building, the chemical energy from your body is converted into potential energy as you gain height. - The total energy before you climb equals the total energy after you climb, just in different forms. - In the case of a compressed spring, mechanical work input is stored as potential energy within the spring. Because energy is conserved, any transformation from chemical energy to potential energy or from mechanical work to potential energy is perfectly balanced, which is why there are no net energy gains or losses in isolated systems.
Relativistic Mass
Relativistic mass refers to how the mass of an object increases with its energy. According to Einstein's theory of relativity, if your energy increases, your mass will increase too. This is represented with the famous equation \( E = mc^2 \):- Here, \( \Delta m = \frac{\Delta E}{c^2} \), showing the mass increase comes from the energy increase.- The speed of light \( c \) is a very large number (\( 3 \times 10^8 \, \text{m/s} \)), meaning any energy increase translates to a very, very small change in mass.When climbing 30 meters, the energy gained is converted into an imperceptibly small increase in mass because \( c^2 \) is so large, making \( \Delta m \) almost zero. Similarly, when compressing a spring, the change in energy distribution results in a tiny adjustable mass, not detectable on a regular scale.
Spring Compression
Spring compression is a common phenomenon in physics studies relating to potential energy storage. When a spring is compressed, it stores energy in the form of potential energy, calculated using:- \( U = \frac{1}{2}kx^2 \), where: - \( k \) is the spring constant (force per unit displacement), measured in N/m. - \( x \) is the compression (in meters).For example, if a spring compressed by 6 cm has a force constant of 200 N/cm, it stores energy, altering its mass. However, converting this potential energy to mass change results in a difference so minuscule, around nanogram levels, it is impossible to detect or feel. This is undeniably due to the large denominator \( c^2 \) in the conversion, emphasizing energy distribution rather than noticeable mass accumulation.

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Most popular questions from this chapter

The negative pion \(\left(\pi^{-}\right)\) is an unstable particle with an average lifetime of \(2.60 \times 10^{-8} \mathrm{s}\) (measured in the rest frame of the pion). (a) If the pion is made to travel at very high speed relative to a laboratory, its average lifetime is measured in the laboratory to be \(4.20 \times 10^{-7} \mathrm{s}\) . Calculate the speed of the pion expressed as a fraction of \(c .\) (b) What distance, measured in the laboratory, does the pion travel during its average lifetime?

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