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55m A person who weighs \(670 \mathrm{N}\) steps onto a spring scale in the bathroom, and the spring compresses by \(0.79 \mathrm{cm} .\) (a) What is the spring constant? (b) What is the weight of another person who compresses the spring by \(0.34 \mathrm{cm} ?\)

Short Answer

Expert verified
(a) The spring constant is approximately \(84810.13\,\text{N/m}\). (b) The weight is approximately \(288\,\text{N}\).

Step by step solution

01

Understanding Hooke's Law

Hooke's Law states that the force exerted by a spring is directly proportional to the displacement of the spring from its equilibrium position. Mathematically, it is expressed as \(F = kx\), where \(F\) is the force applied, \(k\) is the spring constant, and \(x\) is the displacement of the spring.
02

Converting Units

Before we proceed with calculations, convert the displacement from centimeters to meters because the standard unit of length in physics equations is meters. So, \(0.79\,\text{cm} = 0.0079\,\text{m}\) and \(0.34\,\text{cm} = 0.0034\,\text{m}\).
03

Calculating the Spring Constant (Part a)

Use Hooke's Law to find the spring constant. With a force of \(670\,\text{N}\) and a displacement of \(0.0079\,\text{m}\), the spring constant \(k\) can be calculated as follows: \[k = \frac{F}{x} = \frac{670}{0.0079} \approx 84810.13\,\text{N/m}.\]
04

Solving for the New Force (Part b)

To find the force (weight) of the second person, use the spring constant found in part (a). Apply Hooke's Law with the new displacement of \(0.0034\,\text{m}\): \[F = kx = 84810.13 \times 0.0034 \approx 288\,\text{N}.\]

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Key Concepts

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

Spring Constant
The spring constant, often symbolized as \( k \), is a measure of a spring's stiffness. It tells us how much force is needed to compress or stretch a spring by a certain length. In Hooke's Law, the spring constant is central to determining the relationship between force and displacement. The larger the spring constant, the stiffer the spring, meaning it requires more force to produce a certain displacement.
This value is generally expressed in Newtons per meter (N/m). You can think of it as how strongly a spring resists deformation. For instance, a spring with a constant of 84810.13 N/m, as calculated from the exercise, is quite stiff and would need a substantial force to compress or extend it by one meter.
Force and Displacement
Force and displacement are closely linked through Hooke's Law, which is expressed as \( F = kx \). Here, \( F \) represents the force applied to the spring, \( k \) is the spring constant, and \( x \) is the displacement from the spring's natural length.
When force is applied to an object, such as stepping onto a spring scale, it causes the spring to compress or stretch, which is termed displacement. The amount of displacement depends on how much force is applied and how stiff the spring is. For example, in the exercise, stepping onto the spring applies a force of 670 N and results in a displacement of 0.0079 m.
This principle helps us measure forces such as weight by observing how much a spring compresses under a known force. Understanding this relationship allows for practical applications in a range of devices, including weight scales.
Unit Conversion
Converting units is essential when working with physics equations to ensure that calculations remain accurate. In the context of weight measurement using a spring scale, it's important to convert displacement measurements from centimeters to meters.
Since the standard unit of length in these calculations is meters, even small differences in units can greatly affect the results. For instance, the displacement of 0.79 cm must be converted to meters by dividing by 100, resulting in 0.0079 meters.
Unit conversion ensures consistency and helps in maintaining the integrity of calculations when using Hooke's Law and similar equations. Always remember to align your units to match the standard as required by the equation you're working with.
Weight Measurement
Weight measurement using a spring scale involves applying Hooke's Law. In the exercise, a spring scale measures weight by determining how much a spring compresses under the weight of a person.
The force exerted by a person's weight is counterbalanced by the spring's resistance. The compressed distance (or displacement) allows us to calculate the weight, provided we know the spring constant. For instance, with a given spring constant of 84810.13 N/m, the exercise computed a second person's weight as around 288 N when the spring compressed by 0.0034 m.
This method effectively turns the physical action of stepping on a scale into measurable data, capturing precise weight measurements through the spring's mechanical properties. Understanding and applying these principles allows us to accurately gauge weight in everyday situations.

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Most popular questions from this chapter

Between each pair of vertebrae in the spinal column is a cylindrical disc of cartilage. Typically, this disc has a radius of about \(3.0 \times 10^{-2} \mathrm{m}\) and a thickness of about \(7.0 \times 10^{-3} \mathrm{m} .\) The shear modulus of cartilage is \(1.2 \times 10^{7} \mathrm{N} / \mathrm{m}^{2} .\) Suppose that a shearing force of magnitude \(11 \mathrm{N}\) is applied parallel to the top surface of the disc while the bottom surface remains fixed in place. How far does the top surface move relative to the bottom surface?

A copper rod (length \(=2.0 \mathrm{m},\) radius \(\left.=3.0 \times 10^{-3} \mathrm{m}\right)\) hangs down from the ceiling.A 9.0 -kg object is attached to the lower end of the rod. The rod acts as a "spring," and the object oscillates vertically with a small amplitude. Ignoring the rod's mass, find the frequency \(f\) of the simple harmonic motion.

Two metal beams are joined together by four rivets, as the drawing indicates. Each rivet has a radius of \(5.0 \times 10^{-3} \mathrm{m}\) and is to be exposed to a shearing stress of no more than \(5.0 \times 10^{8}\) Pa. What is the maximum tension \(\overrightarrow{\mathbf{T}}\) that can be applied to each beam, assuming that each rivet carries one-fourth of the total load?

An archer, about to shoot an arrow, is applying a force of \(+240 \mathrm{N}\) to a drawn bowstring. The bow behaves like an ideal spring whose spring constant is \(480 \mathrm{N} / \mathrm{m} .\) What is the displacement of the bowstring?

Multiple-Concept Example 6 presents a model for solving this problem. As far as vertical oscillations are concerned, a certain automobile can be considered to be mounted on four identical springs, each having a spring constant of \(1.30 \times 10^{5} \mathrm{N} / \mathrm{m} .\) Four identical passengers sit down inside the car, and it is set into a vertical oscillation that has a period of 0.370 s. If the mass of the empty car is 1560 kg, determine the mass of each passenger. Assume that the mass of the car and its passengers is distributed evenly over the springs.

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