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\(\bullet\) \(\bullet\) A spring is 17.0 \(\mathrm{cm}\) long when it is lying on a table. One end is then attached to a hook and the other end is pulled by a force that increases to 25.0 \(\mathrm{N}\) , causing the spring to stretch to a length of 19.2 \(\mathrm{cm} .\) (a) What is the force constant of this spring? (b) How much work was required to stretch the spring from 17.0 \(\mathrm{cm}\) to 19.2 \(\mathrm{cm}\) (c) How long will the spring be if the 25 \(\mathrm{N}\) force is replaced by a 50 \(\mathrm{N}\) force?

Short Answer

Expert verified
(a) The spring constant is 1136.36 N/m. (b) The work done is 0.275 J. (c) The new length is 21.4 cm.

Step by step solution

01

Determine the Force Constant (Spring Constant)

To find the force constant, use Hooke's Law, which states that the force required to stretch or compress a spring by a distance \( x \) from its natural length is proportional to that distance. Mathematically, this is expressed as \( F = kx \), where \( F \) is the force applied, \( k \) is the spring constant, and \( x \) is the displacement from the original length. 1. **Calculate the displacement**, \( x = 19.2 \, ext{cm} - 17.0 \, ext{cm} = 2.2 \, ext{cm} = 0.022 \, ext{m} \).2. **Rearrange Hooke's Law** to solve for \( k \): \[ k = \frac{F}{x} = \frac{25.0 \, \text{N}}{0.022 \, \text{m}} \]3. **Calculate \( k \):** \[ k = 1136.36 \, \text{N/m} \]
02

Calculate the Work Done in Stretching the Spring

The work done on a spring is given by the formula: \[ W = \frac{1}{2}kx^2 \]where \( W \) is the work done, \( k \) is the spring constant, and \( x \) is the displacement.1. **Use the spring constant** from Step 1: \( k = 1136.36 \, \text{N/m} \)2. **Use the displacement**: \( x = 0.022 \, \text{m} \)3. **Calculate the work done**: \[ W = \frac{1}{2} \times 1136.36 \, \text{N/m} \times (0.022 \, \text{m})^2 \] \[ W = 0.275 \, \text{J} \]
03

Predict the Length of Spring with 50 N Force

To determine the new length of the spring under a 50.0 N force:1. **Use Hooke's Law** with the new force (\( F = 50.0 \, \text{N} \)) and previously calculated spring constant (\( k = 1136.36 \, \text{N/m} \)) to find the new displacement \( x \). \( x = \frac{F}{k} = \frac{50.0 \, \text{N}}{1136.36 \, \text{N/m}} = 0.044 \, \text{m} \)2. **Determine the new length of the spring** by adding the displacement to the original length: \[ \text{Length} = 17.0 \, \text{cm} + 0.044 \, \text{m} = 21.4 \, \text{cm} \] 3. **Convert the displacement to cm**: \( 0.044 \, \text{m} = 4.4 \, \text{cm} \) 4. **Calculate total length**: \( 17.0 \, \text{cm} + 4.4 \, \text{cm} = 21.4 \, \text{cm} \)

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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, also known as the force constant, is an essential parameter in physics that describes how stiff a spring is. It is denoted by the symbol \( k \). This parameter plays a crucial role when you apply Hooke's Law. Hooke's Law is a principle that tells us the force needed to extend or compress a spring is directly proportional to the distance it is stretched or compressed from its natural length.

In more straightforward terms, if a spring is harder to stretch, it will have a higher spring constant. So, the value of \( k \) represents the stiffness of the spring. The formula provided by Hooke's Law is \( F = kx \), where:
  • \( F \) is the force applied in Newtons (N).
  • \( k \) is the spring constant measured in Newtons per meter (N/m).
  • \( x \) is the displacement or change in length from the spring's natural length, measured in meters (m).
To calculate the spring constant, simply rearrange the formula to \( k = \frac{F}{x} \). This ratio results in the amount of force applied per unit displacement, indicating how resistant the spring is to deformation.
In the context of the exercise, when the spring stretches from 17.0 cm to 19.2 cm under a force of 25.0 N, the displacement \( x \) is 0.022 m. Using the Hooke's Law rearrangement, the spring constant \( k \) was found to be 1136.36 N/m.
Work Done on a Spring
The work done on a spring during stretching or compressing is a measure of the energy transferred to the spring. This concept is crucial in understanding how energy is stored mechanically in the spring. The work done is calculated using the formula:

\[ W = \frac{1}{2}kx^2 \]

Where:
  • \( W \) is the work done, measured in Joules (J).
  • \( k \) is the spring constant, already determined from calculations (1136.36 N/m in this exercise).
  • \( x \) is the displacement from the spring’s relaxed position, measured in meters (0.022 m in the exercise).
By using this equation, we can derive the total amount of energy required to either compress or extend the spring by a certain amount. This energy is stored in the form of potential energy within the spring, which can later be released to perform work. In the case of the spring from the exercise, the work done to stretch it from 17.0 cm to 19.2 cm is 0.275 Joules.
Understanding the work done on a spring provides us with insights into energy conservation and mechanical processes. It's a pivotal topic in both educational and practical applications in physics.
Force and Displacement
Force and displacement are key components when working with springs, especially in the context of Hooke's Law and spring mechanics. When a force is applied to a spring, it causes a change in the spring's length, known as displacement. Understanding the relationship between these two factors helps us predict how a spring will behave under different forces.

When you apply a force (\( F \)) to a spring, it stretches or compresses by a certain distance, which is the displacement (\( x \)). This concept is practically observed when we perform experiments like the one in our exercise, where a force of 25.0 N caused the spring to elongate from 17.0 cm to 19.2 cm, resulting in a displacement of 0.022 m.

Hooke's Law provides a straightforward way to relate force and displacement with the spring constant, represented by the equation \( F = kx \). This linear relationship tells us that, for small displacements, the spring's response is predictable and proportional to the applied force.
  • Higher forces cause greater displacements if the spring constant remains the same.
  • A stiffer spring (higher \( k \)) will show less displacement for the same force compared to a spring with a lower \( k \).
In the exercise scenario, when the force was increased to 50.0 N, the corresponding displacement was calculated, allowing us to predict the new length of the spring. Understanding these concepts is fundamental in physics and engineering disciplines for designing systems involving spring mechanics.

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Most popular questions from this chapter

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