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A spring stretches by 0.018 m when a 2.8-kg object is suspended from its end. How much mass should be attached to this spring so that its frequency of vibration is \(f=3.0 \mathrm{Hz} ?\)

Short Answer

Expert verified
Attach approximately 2.695 kg to achieve 3.0 Hz.

Step by step solution

01

Understand the Problem

We are given a spring that stretches by 0.018 m when a 2.8 kg mass is attached. We need to find out what mass will make this system vibrate with a frequency of 3.0 Hz.
02

Apply Hooke's Law

According to Hooke's Law, the force exerted by a spring is related to its displacement by the equation: \( F = kx \), where \( k \) is the spring constant and \( x \) is the displacement. We know \( F = mg = 2.8 \times 9.8 \), and \( x = 0.018 \). Thus, \( k = \frac{F}{x} = \frac{2.8 \times 9.8}{0.018} \approx 1523.33 \, \text{N/m} \).
03

Use the Formula for Frequency of a Spring-Mass System

The frequency of a mass-spring system is given by the formula \( f = \frac{1}{2\pi}\sqrt{\frac{k}{m}} \). We need to find the mass \( m \) that will give a frequency \( f = 3.0 \, \text{Hz} \).
04

Solve for Mass \( m \)

Rearranging the frequency formula to solve for mass gives us: \( m = \frac{k}{(2\pi f)^2} \). Substituting the known values, \( m = \frac{1523.33}{(2\pi \times 3.0)^2} \approx 2.695 \, \text{kg} \).
05

Verify the Solution

Check the calculation: Using \( m = \frac{k}{(2\pi f)^2} \) again, confirm \( m \approx 2.695 \) ensures the frequency \( f \) equals 3.0 Hz. This verifies our solution is consistent with the given conditions.

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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 under load. It states that the force exerted by a spring is directly proportional to the displacement it undergoes. This relationship can be expressed mathematically as:
  • \( F = kx \)
Here, \( F \) is the force applied to the spring, \( k \) is the spring constant, and \( x \) is the displacement from its original position. The spring constant \( k \) is a vital part of this equation, representing the stiffness of the spring. A higher spring constant indicates a stiffer spring that doesn't stretch easily.
In practical terms, Hooke's Law helps understand how much force is needed to stretch or compress a spring by a given amount. This principle is not only crucial in physics but also in engineering applications, where precise control of mechanical systems is required.
Spring Constant
The spring constant, denoted by \( k \), measures a spring's stiffness. It determines how much force is needed to extend or compress a spring by a certain distance. In the formula \( F = kx \), the spring constant \( k \) tells you how much force (\( F \)) is needed for each unit of displacement (\( x \)).
The unit of the spring constant is newtons per meter (N/m). A larger \( k \) means a stiffer spring, requiring more force for the same displacement. In our exercise, using the data with a 2.8 kg mass stretching the spring by 0.018 m, the spring constant calculated was approximately 1523.33 N/m.
Understanding the spring constant is essential for tasks like designing suspension systems or calculating oscillations in mechanical setups. It provides insights into how a spring will behave when forces are applied, which is crucial for safety and performance in applications ranging from vehicle suspensions to measuring devices.
Frequency of Vibration
Frequency of vibration refers to how often an oscillating system completes a cycle per unit time. In the context of a spring-mass system, it indicates how quickly the mass goes back and forth. It is measured in hertz (Hz), where one hertz is one complete cycle per second.
The frequency \( f \) of a simple harmonic oscillator like a spring-mass system is given by the formula:
  • \( f = \frac{1}{2\pi} \sqrt{\frac{k}{m}} \)
Here, \( k \) is the spring constant, and \( m \) is the mass attached to the spring. This equation shows that the frequency is influenced directly by the spring constant and inversely by the mass. Thus, increasing the mass decreases the frequency, while a stronger spring (higher \( k \)) increases the frequency.
In our problem, given a desired frequency of 3.0 Hz, we can use this relationship to calculate the appropriate mass that needs to be attached to achieve such vibrations. This involves solving the equation by rearranging it to find \( m \), showcasing how changes in \( m \) or \( k \) affect the system's behavior.

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Most popular questions from this chapter

A vertical spring (spring constant 5 112 N/m) is mounted on the fl oor. A 0.400-kg block is placed on top of the spring and pushed down to start it oscillating in simple harmonic motion. The block is not attached to the spring. (a) Obtain the frequency (in Hz) of the motion. (b) Determine the amplitude at which the block will lose contact with the spring.

In a room that is 2.44 m high, a spring (unstrained length \(=0.30 \mathrm{m}\) ) hangs from the ceiling. A board whose length is \(1.98 \mathrm{m}\) is attached to the free end of the spring. The board hangs straight down, so that its \(1.98-\mathrm{m}\) length is perpendicular to the floor. The weight of the board \((104 \mathrm{N})\) stretches the spring so that the lower end of the board just extends to, but does not touch, the floor. What is the spring constant of the spring?

A 1.0 \times 10 \(^{-3}\) -kg spider is hanging vertically by a thread that has a Young's modulus of \(4.5 \times 10^{9} \mathrm{N} / \mathrm{m}^{2}\) and a radius of \(13 \times 10^{-6} \mathrm{m} .\) Suppose that a \(95-\mathrm{kg}\) person is hanging vertically on an aluminum wire. What is the radius of the wire that would exhibit the same strain as the spider's thread, when the thread is stressed by the full weight of the spider?

The fan blades on a jet engine make one thousand revolutions in a time of 50.0 ms. Determine (a) the period (in seconds) and (b) the frequency (in Hz) of the rotational motion. (c) What is the angular frequency of the blades?

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?

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