/*! 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 12 To measure the static friction c... [FREE SOLUTION] | 91Ó°ÊÓ

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To measure the static friction coefficient between a 1.6-kg block and a vertical wall, the setup shown in the drawing is used. A spring (spring constant = 510 N/m) is attached to the block. Someone pushes on the end of the spring in a direction perpendicular to the wall until the block does not slip downward. The spring is compressed by 0.039 m. What is the coefficient of static friction?

Short Answer

Expert verified
The coefficient of static friction is approximately 0.79.

Step by step solution

01

Identify Given Values

We are given the mass of the block, \( m = 1.6 \) kg, the spring constant, \( k = 510 \) N/m, and the spring compression, \( x = 0.039 \) m. We need to find the coefficient of static friction, \( \mu_s \).
02

Calculate the Force Exerted by the Spring

The force exerted by the spring can be found using Hooke's Law, which states \( F_{spring} = k \cdot x \). Substituting the given values, \( F_{spring} = 510 \times 0.039 = 19.89 \) N.
03

Determine the Gravitational Force

The gravitational force acting on the block is given by \( F_{gravity} = m \cdot g \), where \( g = 9.8 \) m/s² (the acceleration due to gravity). Substituting the given mass, \( F_{gravity} = 1.6 \times 9.8 = 15.68 \) N.
04

Relate Static Friction and Spring Force

Since the block does not slip, the static friction force must balance the weight of the block. Therefore, the normal force is provided by the spring, and the static friction force can be written as \( f_s = \mu_s \cdot F_{spring} \). Additionally, we have \( f_s = F_{gravity} \).
05

Solve for the Coefficient of Static Friction

Set the expressions for \( f_s \) equal: \( \mu_s \cdot 19.89 = 15.68 \) and solve for \( \mu_s \). Thus, \( \mu_s = \frac{15.68}{19.89} \approx 0.79 \).

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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 provides a fundamental principle connecting the force in a spring to the distance it is stretched or compressed. It tells us that the force exerted by a spring is directly proportional to its change in length from its original position. This is expressed through the equation: \[ F_{spring} = k \times x \]where:
  • \( F_{spring} \) is the force exerted by the spring,
  • \( k \) is the spring constant (a measure of the stiffness of the spring),
  • \( x \) is the displacement of the spring from its equilibrium position.
The key takeaway is that as the spring is stretched or compressed more, the force grows stronger, provided the deformation remains within the elastic limit of the spring.
In the given exercise, Hooke's Law helps us calculate the force required to compress the spring a certain distance. Knowing this force helps in calculating other forces interacting with our block on the wall.
Gravitational Force
Gravitational force is one of the fundamental forces in nature. It acts on all objects with mass and pulls them towards the center of the Earth. The force of gravity acting on an object is calculated by the formula:\[ F_{gravity} = m \times g \]where:
  • \( F_{gravity} \) is the gravitational force,
  • \( m \) is the mass of the object,
  • \( g \) is the acceleration due to gravity, approximately \( 9.8 \text{ m/s}^2 \) on Earth.
In the scenario provided, the gravitational force is the weight of the block pulling it downward. Understanding gravitational force is crucial as it determines how much static friction is required to keep the block from sliding down the wall.
Coefficient of Static Friction
The coefficient of static friction, denoted as \( \mu_s \), is a dimensionless number that describes the ratio of the maximum static frictional force to the normal force acting on an object. It's a measure of how much force is needed to overcome static friction and start moving the object.The static friction force can be calculated using:\[ f_s = \mu_s \times F_{normal} \]However, in this exercise, because the block is against a vertical wall, the role of the normal force is played by the force exerted by the spring, making:\[ f_s = \mu_s \times F_{spring} \]In balance, it equals the gravitational force to prevent the block from slipping down:\[ \mu_s \times 19.89 = 15.68 \]Solving for \( \mu_s \) gives us the static friction coefficient needed to stop the block from sliding. This coefficient depends on the surfaces in contact and their roughness.
Spring Constant
The spring constant, symbolized as \( k \), is a parameter that quantifies the stiffness of a spring. The larger the value of \( k \), the stiffer the spring and the more force it takes to compress or stretch it.Expressed in Newtons per meter (N/m), it tells you how much force is needed to change the spring’s length by a certain amount:\[ F_{spring} = k \times x \]In our exercise, the spring constant is given as \( 510 \text{ N/m} \), indicating how much force needs to be applied to compress the spring by a meter. This is useful to understand how much force the spring has in balancing the forces acting on the block.A high spring constant means the spring pushes back more, which contributes significantly to determining the coefficient of static friction when paired with the gravitational force.

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Most popular questions from this chapter

A cylindrically shaped piece of collagen (a substance found in the body in connective tissue) is being stretched by a force that increases from 0 to \(3.0 \times 10^{-2} \mathrm{N}\). The length and radius of the collagen are, respectively, 2.5 and \(0.091 \mathrm{cm},\) and Young's modulus is \(3.1 \times 10^{6} \mathrm{N} / \mathrm{m}^{2}\). (a) If the stretching obeys Hooke's law, what is the spring constant \(k\) for collagen? (b) How much work is done by the variable force that stretches the collagen? (See Section 6.9 for a discussion of the work done by a variable force.)

A vertical ideal spring is mounted on the floor and has a spring constant of \(170 \mathrm{N} / \mathrm{m}\). A \(0.64-\mathrm{kg}\) block is placed on the spring in two different ways. (a) In one case, the block is placed on the spring and not released until it rests stationary on the spring in its equilibrium position. Determine the amount (magnitude only) by which the spring is compressed. (b) In a second situation, the block is released from rest immediately after being placed on the spring and falls downward until it comes to a momentary halt. Determine the amount (magnitude only) by which the spring is now compressed.

A 0.60-kg metal sphere oscillates at the end of a vertical spring. As the spring stretches from 0.12 to 0.23 m (relative to its unstrained length), the speed of the sphere decreases from 5.70 to 4.80 m/s. What is the spring constant of the spring?

ao \(A\) spring lies on a horizontal table, and the left end of the spring is attached to a wall. The other end is connected to a box. The box is pulled to the right, stretching the spring. Static friction exists between the box and the table, so when the spring is stretched only by a small amount and the box is released, the box does not move. The mass of the box is \(0.80 \mathrm{kg},\) and the spring has a spring constant of \(59 \mathrm{N} / \mathrm{m} .\) The coefficient of static friction between the box and the table on which it rests is \(\mu_{\mathrm{s}}=0.74\) How far can the spring be stretched from its unstrained position without the box moving when it is released?

A die is designed to punch holes with a radius of \(1.00 \times 10^{-2} \mathrm{m}\) in a metal sheet that is \(3.0 \times 10^{-3} \mathrm{m}\) thick, as the drawing illustrates. To punch through the sheet, the die must exert a shearing stress of \(3.5 \times 10^{8} \mathrm{Pa} .\) What force \(\overrightarrow{\mathbf{F}}\) must be applied to the die?

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