/*! 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 71 Running Shoes The soles of a pop... [FREE SOLUTION] | 91Ó°ÊÓ

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Running Shoes The soles of a popular make of running shoe have a force constant of \(2.0 \times 10^{5} \mathrm{N} / \mathrm{m} .\) Treat the soles as ideal springs for the following questions. (a) If a \(62-\mathrm{kg}\) person stands in a pair of these shoes, with her weight distributed equally on both feet, how much does she compress the soles? (b) How much energy is stored in the soles of her shoes when she's standing?

Short Answer

Expert verified
(a) 0.00152 m; (b) 0.115 J.

Step by step solution

01

Determine the weight of the person

The weight of the person is given by the equation \( F = mg \), where \( m = 62 \text{ kg} \) is the mass and \( g = 9.8 \text{ m/s}^2 \) is the acceleration due to gravity. Calculate \( F = 62 \times 9.8 \).
02

Apply Hooke's Law to find the compression

Using Hooke's Law, \( F = kx \), where \( k = 2.0 \times 10^5 \text{ N/m} \) is the force constant and \( x \) is the compression. Solve for \( x \): \( x = \frac{F}{k} \). Since the weight is distributed equally on both feet, divide the calculated force by 2.
03

Calculate the energy stored in the soles

The potential energy stored in the soles is given by \( PE = \frac{1}{2}kx^2 \). Use the compression found in Step 2 to compute the energy.

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Key Concepts

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

Force Constant
In the world of springs, the force constant, also known as the spring constant, is a vital parameter. Represented by the symbol \(k\), it tells us how stiff or flexible a spring is. A high force constant means the spring is quite stiff, and a low force constant means it is more flexible.
This concept is central to Hooke's Law, which explains the relationship between the force applied to a spring and the amount it is stretched or compressed. Hooke's Law can be expressed mathematically as:
  • \(F = kx\)
In this formula:
  • \(F\) stands for the force exerted on the spring.
  • \(k\) is the force constant.
  • \(x\) is the displacement or compression of the spring.
By understanding the force constant, you're equipped to predict how a spring will behave under different forces. It's an essential concept for determining just how much energy a spring can store and how much it can exert when released.
Compression in Springs
When a force is applied to a spring, it either stretches or compresses, depending on the direction of the force. The change in distance from the spring's original shape is known as compression (if it's shorter) or extension (if it's longer). In our exercise, we focus on compression.
To calculate the compression in springs using Hooke's Law, we rearrange the formula \(F = kx\) to solve for \(x\):
  • \(x = \frac{F}{k}\)
This tells us the amount of compression (\(x\)) that happens under a certain force (\(F\)).
  • "\(F\)" refers to the force applied, equivalent to half the weight of the person if the force is equally distributed on both shoes.
  • "\(k\)" is the force constant, determining how much the spring reacts to the applied force.
This simple calculation helps us understand how different materials resist deformation. It enables engineers to design products like running shoes with soles that can efficiently absorb impacts.
Potential Energy in Springs
Springs are capable of storing energy when they are compressed or stretched, a concept known as potential energy. The beauty of this energy form lies in its ability to be converted into kinetic energy, or energy of motion, when the compression or extension is released.The potential energy stored in a spring, especially when using ideal conditions, can be calculated with the formula:
  • \(PE = \frac{1}{2}kx^2\)
Here, potential energy (\(PE\)) is directly related to:
  • "\(k\)", the force constant or spring stiffness.
  • "\(x\)", the amount of compression or stretch in the spring.
The importance of potential energy in springs is significant in various applications. For instance, in running shoes, the soles are designed to store energy efficiently and release it during movements, helping runners conserve energy and improve performance. Understanding the principles of potential energy ensures that these products are both effective and safe.

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Most popular questions from this chapter

Predict/Explain When a ball of mass \(m\) is dropped from rest from a height \(h,\) its kinetic energy just before landing is \(K\). Now, suppose a second ball of mass \(4 m\) is dropped from rest from a height \(h / 4 .\) (a) Just before ball 2 lands, is its kinetic energy \(4 K, 2 K, K, K / 2,\) or \(K / 4 ?\) (b) Choose the best explanation from among the following: I. The two balls have the same initial energy. II. The more massive ball will have the greater kinetic energy. III. The reduced drop height results in a reduced kinetic energy.

The work required to stretch a certain spring from an elongation of \(4.00 \mathrm{cm}\) to an elongation of \(5.00 \mathrm{cm}\) is \(30.5 \mathrm{J}\). (a) Is the work required to increase the elongation of the spring from 5.00 \(\mathrm{cm}\) to \(6.00 \mathrm{cm}\) greater than, less than, or equal to \(30.5 \mathrm{J}\) ? Explain. (b) Verify your answer to part (a) by calculating the required work.

Jeff of the Jungle swings on a \(7.6-\mathrm{m}\) vine that initially makes an angle of \(37^{\circ}\) with the vertical. If Jeff starts at rest and has a mass of \(78 \mathrm{kg}\), what is the tension in the vine at the lowest point of the swing?

BIO A Flea's Jump The resilin in the upper leg (coxa) of a flea has a force constant of about \(26 \mathrm{N} / \mathrm{m}\), and when the flea cocks its jumping legs, the resilin in each leg is stretched by approximately \(0.10 \mathrm{mm}\). Given that the flea has a mass of \(0.50 \mathrm{mg}\) and that two legs are used in a jump, estimate the maximum height a flea can attain by using the energy stored in the resilin. (Assume the resilin to be an ideal spring.)

Two blocks, each of mass \(m\), are connected on a frictionless horizontal table by a spring of force constant \(k\) and equilibrium length \(L\). Find the maximum and minimum separation between the two blocks in terms of their maximum speed, \(v_{\max }\), relative to the table. (The two blocks always move in opposite directions as they oscillate back and forth about a fixed position.)

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