/*! 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 34 The 4 -kg smooth cylinder is sup... [FREE SOLUTION] | 91Ó°ÊÓ

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The 4 -kg smooth cylinder is supported by the spring having a stiffness of \(k_{A B}=120 \mathrm{~N} / \mathrm{m}\). Determine the velocity of the cylinder when it moves downward \(s=0.2 \mathrm{~m}\) from its equilibrium position, which is caused by the application of the force \(F=60 \mathrm{~N}\). Prob. 13-34

Short Answer

Expert verified
The velocity of the cylinder when it moves downward 0.2 m from its equilibrium position is 4.17 m/s.

Step by step solution

01

Formulate the initial Energy

First, when the cylinder is at equilibrium position, the applied force equals the spring force. According to Hooke's Law, \( F = k * s \). By setting these two forces equal to each other, you can solve for \( s \): \( 60 = 120 * s \), resulting in \( s = 60 / 120 = 0.5 m \) being the initial displacement.
02

Determine the Applied Work

The work done by the applied force and the work done by the weight of the cylinder are represented by the formula \( W = F * s \). In this case, the work done by the applied force is \( W_f = F * s = 60 * 0.2 = 12 J \) and the work done by the weight of the cylinder is \( W_w = m * g * s = 4 * 9.81 * 0.2 = 7.848 J \).
03

Calculate the initial potential energy

The potential energy of the spring at the initial position can be calculated by the formula \( U = 1 / 2 * k * s^2 \). Here, \( U = 1 / 2 * 120 * (0.5)^2 = 15 J \).
04

Calculate total final energy (potential energy + kinetic energy)

The total energy at the final position, when the spring is further compressed by 0.2 m, would be the total work done (Work done by applied force + Work done by weight) added with the initial potential energy of the spring. That gives, \( E = W_f + W_w + U = 12 + 7.848 + 15 = 34.848 J \).
05

Calculate the final velocity

At the final position, all of the energy will be kinetic energy because the cylinder will be in motion and the spring will be at its maximum compression. The kinetic energy is represented by the formula \( K = 1 / 2 * m * v^2 \). So, rearranging to solve for \( v \), we get \( v = sqrt((2 * K) / m) \). Substituting the values gives \( v = sqrt((2 * 34.848) / 4) = sqrt(17.424) = 4.17 m/s \).

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Key Concepts

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

Hooke's Law
Understanding Hooke's Law is foundational for analyzing spring systems. It is a principle stating that the force needed to extend or compress a spring by some distance is proportional to that distance. Mathematically, Hooke's Law is expressed as \( F = k \times x \), where \( F \) is the force applied to the spring, \( k \) is the spring constant, and \( x \) is the displacement of the spring from its original equilibrium position.

When applied to our exercise, the force \( F \) given by the problem is used to find the equilibrium displacement \( s \) for the cylinder when it is balanced solely by the spring's force. With Hooke's Law, we can see that this equilibrium is reached when the applied force equals the force exerted by the spring. This relationship is critical when we begin to account for the energy stored in the spring as potential energy, which is later converted to kinetic energy – leading us to the other concepts.
Kinetic Energy
Kinetic energy is the energy of motion. For any object in motion with mass \( m \) and velocity \( v \), the kinetic energy \( K \) is given by the equation \( K = \frac{1}{2} \times m \times v^2 \). This energy is a scalar quantity, which means it has magnitude but no direction, and it is always a positive value.

In the context of our exercise, we're interested in the kinetic energy of the cylinder at the point it has traveled a certain distance \( s \) from the equilibrium position. Initially, the spring system has potential energy, and as the cylinder moves, that potential energy is converted into kinetic energy. This directly contributes to the velocity of the cylinder which we are aiming to calculate. Through the relationship of kinetic energy to velocity, we can derive the latter using the value for \( K \) obtained from the energy principles.
Potential Energy
Potential energy is stored energy – energy that an object has due to its position, shape, or state. For a spring system, the potential energy, often referred to as elastic potential energy, depends on the displacement and the spring constant, as per the equation \( U = \frac{1}{2} \times k \times s^2 \).

In our exercise, we calculate the initial potential energy of the spring using the equilibrium displacement determined through Hooke's Law. This initial value of potential energy is a crucial piece in understanding the work-energy principle, as it represents the energy that will be available for conversion into kinetic energy as the spring is compressed further and the cylinder accelerates downward.
Work-Energy Principle
The work-energy principle is an essential concept in physics that connects the work done on an object with the change in its energy. According to this principle, the work done by all forces acting on an object will result in a corresponding change in the object's kinetic energy. We can express the principle through the equation: \( W_{total} = \triangle K \), where \( W_{total} \) is the total work done on the object, and \( \triangle K \) is the change in kinetic energy.

In the step-by-step solution, we applied this principle by calculating the work done by the external force and by gravity. By adding these works to the initial potential energy of the spring, we obtain the total final energy, which must all be kinetic when the spring is at maximum compression and the cylinder is moving. We then used this total energy to find the cylinder’s velocity at the point of maximum compression, demonstrating the practical application of the work-energy principle in solving real-world physics problems.

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