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Triple Choice The potential energy of a stretched spring is positive. Is the potential energy of a compressed spring positive, negative, or zero? Explain.

Short Answer

Expert verified
The potential energy of a compressed spring is positive.

Step by step solution

01

Understanding Potential Energy in Springs

Potential energy (PE) in a spring, whether stretched or compressed, is determined by Hooke's Law which states that PE is proportional to the displacement squared. The formula for potential energy in a spring is: \[ PE = \frac{1}{2} k x^2 \] where \( k \) is the spring constant and \( x \) is the displacement from the equilibrium position.
02

Analyzing the Formula

In the formula \( PE = \frac{1}{2} k x^2 \), note that \( x^2 \) is always positive regardless of whether the spring is compressed or stretched because squaring a number makes it positive. This means that the potential energy will always be positive although the displacement \( x \) can be either positive (stretched) or negative (compressed).
03

Conclusion on Compressed Springs

For a compressed spring, the displacement \( x \) is negative, but the potential energy \( PE \) remains positive because \( x^2 \) is always positive. Therefore, the potential energy of a compressed spring is positive.

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Key Concepts

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

Hooke's Law
Hooke's Law is a fundamental principle in physics that describes the behavior of springs. It states that the force needed to extend or compress a spring is directly proportional to the displacement of the spring from its original position.
This relationship is expressed mathematically as:
  • F = -kx
Here, the force (F) is negative, indicating that it is a restoring force, meaning it works to return the spring to its equilibrium (or original) position.
The variable 'k' represents the spring constant, and 'x' is the displacement. Hooke's Law helps us understand not just force, but also how potential energy is stored in a spring. When you stretch or compress a spring, you are storing energy in the form of potential energy. This energy is released when the spring returns to its original position, making Hooke's Law crucial for understanding systems involving springs and potential energy.
Spring Constant
The spring constant, denoted by 'k,' is an important value in Hooke’s Law.
It represents the stiffness of a spring. The larger the spring constant, the stiffer the spring is, which means more force is required to stretch or compress it.
  • If a spring is easy to stretch, it has a low spring constant.
  • Conversely, if it's hard to stretch, the spring constant is high.
The spring constant is measured in units of force per unit length, such as Newtons per meter (N/m). This constant is crucial when calculating the potential energy stored in a spring, as shown in the formula:\[ PE = \frac{1}{2} k x^2 \]In practical applications, knowing the spring constant helps in designing systems that require specific levels of elasticity or rigidity, making it a fundamental concept in physics and engineering.
Spring Displacement
Spring displacement refers to the distance a spring is stretched or compressed from its equilibrium position.
This displacement, represented by 'x' in mathematical formulas, is a key factor in determining the force exerted by the spring and the potential energy it stores. In the formula \( PE = \frac{1}{2} k x^2 \), the displacement \'x\' is squared. This squaring means that displacement makes a significant impact on the potential energy stored because even small changes in 'x' can lead to larger changes in the energy value.It's important to note:
  • The displacement can be negative when a spring is compressed, but since it is squared in calculations, it always results in a positive potential energy value.
  • Positive displacement indicates stretching, while negative displacement indicates compression.
Understanding spring displacement is critical when analyzing how springs behave under various physical forces and conditions, helping to predict the energy dynamics of systems that use springs.

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Most popular questions from this chapter

\(\rightarrow\) Apply The potential energy of an object decreases by \(10 \mathrm{~J}\). What is the change in the object's kinetic energy, assuming there is no friction in the system?

A small motor runs a lift that raises a load of bricks weighing \(836 \mathrm{~N}\) to a height of \(10.7 \mathrm{~m}\) in \(23.2 \mathrm{~s}\). Assuming that the bricks are lifted with constant speed, what is the minimum power the motor must produce?

A 65-kg bicyclist rides his 8.8-kg bicycle with a speed of \(14 \mathrm{~m} / \mathrm{s}\). (a) How much work must be done by the brakes to bring the bike and rider to a stop? (b) What is the magnitude of the braking force if the bicycle comes to rest in \(3.5 \mathrm{~m}\) ?

Predict \& Explain You throw a ball upward and let it fall to the ground. Your friend drops an identical ball straight down to the ground from the same height. (a) Is the change in kinetic energy (from just after the ball is released until just before it hits the ground) of your ball greater than, less than, or equal to the change in kinetic energy of your friend's ball? (b) Choose the best explanation from among the following: A. Your friend's ball converts all of its initial energy into kinetic energy. B. Your ball is in the air longer, which results in a greater change in kinetic energy. C. The change in gravitational potential energy is the same for each ball, which means that the change in kinetic energy must also be the same.

Think \& Calculate A pitcher accelerates a \(0.14\)-kg hardball from rest to \(25.5 \mathrm{~m} / \mathrm{s}\) in \(0.075 \mathrm{~s}\). (a) How much work does the pitcher do on the ball? (b) What is the pitcher's power output during the pitch? (c) Suppose the ball reaches \(25.5 \mathrm{~m} / \mathrm{s}\) in less than \(0.075 \mathrm{~s}\). Is the power produced by the pitcher in this case more than, less than, or the same as the power found in part (b)? Explain.

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