Chapter 7: Problem 17
A force of \(f\) N stretches a spring \(d\) m from its natural length. How much work is performed in stretching the spring?
Short Answer
Expert verified
The work performed in stretching the spring is \( \frac{fd}{2} \) Joules.
Step by step solution
01
Understanding Hooke's Law
First, recognize that the force needed to extend or compress a spring by some distance is given by Hooke's law, which states that the force \( F \) is proportional to the displacement \( x \), or \( F = kx \), where \( k \) is the spring constant. In this problem, \( F = f \) when the spring is stretched by \( d \) meters.
02
Express Spring Constant
Since \( F = fd \), we can express the spring constant \( k \) using the equation of Hooke's law: \( f = kd \). Solving for \( k \), we get \( k = \frac{f}{d} \).
03
Setup the Work Integral
Work done in stretching the spring is found by integrating the force over the distance the spring is stretched. The work \( W \) done is given by the integral: \[ W = \int_0^d kxdx \]
04
Solve the Integral
Substitute \( k = \frac{f}{d} \) into the integral, giving: \[ W = \int_0^d \frac{f}{d} x \, dx \]Integrate the equation: \[ W = \frac{f}{d} \left[ \frac{x^2}{2} \right]_0^d \] This simplifies to: \[ W = \frac{f}{d} \cdot \frac{d^2}{2} = \frac{fd}{2} \]
05
Concluding the Calculation
Thus, using the relation above, the work performed in stretching the spring by distance \( d \) meters when a force of \( f \) Newtons is applied, is \( \frac{fd}{2} \) Joules.
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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, commonly denoted as \( k \), is a crucial factor in understanding how springs behave. Essentially, it's a measure of a spring's stiffness or elasticity. When you have a stiff spring, the spring constant \( k \) is larger. Conversely, a more flexible spring has a smaller \( k \). Understanding this helps in predicting how the spring will move when a force is applied.
According to Hooke's Law, the force \( F \) required to stretch a spring is directly proportional to the displacement \( x \) of the spring from its rest position. This is mathematically represented as:
According to Hooke's Law, the force \( F \) required to stretch a spring is directly proportional to the displacement \( x \) of the spring from its rest position. This is mathematically represented as:
- \( F = kx \)
- \( k = \frac{f}{d} \)
Work Integral
The concept of work in physics refers to the amount of energy transferred when a force is applied over a distance. In the case of a spring, calculating this work involves an integral because the force varies with the position. The work done \( W \) when stretching a spring over a distance is determined by the integral of the force with respect to displacement.
For a spring obeying Hooke's Law, the force changes linearly with displacement, creating the need to integrate the expression \( kx \), where \( k \) is the spring constant. The work integral formula looks like this:
For a spring obeying Hooke's Law, the force changes linearly with displacement, creating the need to integrate the expression \( kx \), where \( k \) is the spring constant. The work integral formula looks like this:
- \( W = \int_0^d kx \, dx \)
Force and Displacement
Force and displacement are fundamental in understanding how objects move and interact. In the context of spring mechanics, these two concepts work hand in hand. Force \( F \) refers to a push or pull that changes the object's motion, while displacement \( x \) is the change in position of the object.
When a spring is stretched, it experiences displacement. The relationship between force and displacement is linear for springs, as given by Hooke's Law \( F = kx \). This law implies that:
When a spring is stretched, it experiences displacement. The relationship between force and displacement is linear for springs, as given by Hooke's Law \( F = kx \). This law implies that:
- The greater the displacement, the greater the force required to stretch the spring further.
- The spring gets tougher to stretch as you increase displacement because of the rising force.