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A child with poor table manners is sliding his 250 -g dinner plate back and forth in SHM with an amplitude of 0.100 \(\mathrm{m}\) on a horizontal surface. At a point 0.060 \(\mathrm{m}\) away from equilibrium, the speed of the plate is 0.300 \(\mathrm{m} / \mathrm{s}\) . (a) What is the period? (b) What is the displacement when the speed is 0.160 \(\mathrm{m} / \mathrm{s} ?(\mathrm{c})\) In the center of the dinner plate is a \(10.0-\mathrm{g}\) carrot slice. If the carrot slice is just on the verge of slipping at the endpoint of the path, what is the coefficient of static friction between the carrot slice and the plate?

Short Answer

Expert verified
(a) T ≈ 1.623 s, (b) x ≈ 0.0983 m, (c) μₛ ≈ 0.153.

Step by step solution

01

Identifying Variables for Simple Harmonic Motion (SHM)

The amplitude ( A ) is given as 0.100 m, the displacement ( x ) from equilibrium is 0.060 m, and the speed ( v ) at this point is 0.300 m/s. The mass ( m ) of the plate is 250 g or 0.250 kg. We need to find the period ( T ) for part (a).
02

Calculating Angular Frequency (ω)

In SHM, the speed v at a position x from the equilibrium can be expressed as v = ω\sqrt{A^2 - x^2} . Re-arrange the formula to solve for ω :\[v = ω\sqrt{A^2 - x^2} \Rightarrow ω = \frac{v}{\sqrt{A^2 - x^2}}\]Substitute the given values:\[ ω = \frac{0.300}{\sqrt{0.100^2 - 0.060^2}} \approx 3.872 \text{ rad/s}\]
03

Finding the Period (T)

The period T of the SHM is related to the angular frequency ω by the formula T = \frac{2\pi}{ω} .\[ T = \frac{2\pi}{3.872} \approx 1.623 \text{ s}\]Thus, the period T is approximately 1.623 seconds.
04

Calculating Displacement When Speed is 0.160 m/s

For part (b), we use the relation\[ v = ω\sqrt{A^2 - x^2} \]To find x when v = 0.160 :\[0.160 = 3.872\sqrt{0.100^2 - x^2} \Rightarrow \sqrt{0.100^2 - x^2} = \frac{0.160}{3.872}\]Solving for x :\[0.100^2-x^2 = \left(\frac{0.160}{3.872}\right)^2 \approx 0.00171 \Rightarrow x = \sqrt{0.100^2 - 0.00171} \approx 0.0983 \text{ m}\]
05

Determining Coefficient of Static Friction

For part (c), when the carrot slice is just at the verge of slipping, the force of static friction provides the necessary centripetal force for circular motion at the amplitude: \[ F_{static} = m_c \omega^2 A \]Where m_c = 0.010 ext{ kg} is the mass of the carrot, ω = 3.872 ext{ rad/s} and A = 0.100 ext{ m} .The maximum static friction is \mu_s m_c g .Equate and solve for the coefficient of static friction \mu_s :\[ \mu_s m_c g = m_c \omega^2 A \Rightarrow \mu_s = \frac{ω^2 A}{g} = \frac{3.872^2 \times 0.100}{9.8} \approx 0.153 \]

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Key Concepts

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

Amplitude
In simple harmonic motion (SHM), the amplitude is a crucial concept that defines the extent of motion from its equilibrium position. It's represented by the symbol \(A\) and measures the maximum distance the oscillating object travels from the center. For instance, in our example, the child moves the dinner plate back and forth, reaching an amplitude of 0.100 m. This means the plate moves a total of 0.200 m, 0.100 m in either direction from equilibrium. The amplitude remains constant unless an external force acts upon the system, indicating the energy involved in the motion. Understanding amplitude helps in predicting maximum speed and acceleration, which occur at the equilibrium and extreme positions respectively.
Period of SHM
The period of SHM, denoted as \(T\), is the time taken for one complete cycle of motion. In simple terms, it measures how long it takes for the object to return to its initial position and velocity. For our scenario, the child's dinner plate, the calculated period is approximately 1.623 seconds. The period is independent of amplitude and depends solely on factors like mass and the system constant, such as stiffness in a spring-mass system. The formula \(T = \frac{2\pi}{\omega}\) directly relates period to angular frequency \(\omega\), helping us understand how quickly or slowly the system oscillates.
Coefficient of Static Friction
The coefficient of static friction, symbolized as \(\mu_s\), is pivotal for understanding how one object resists sliding over another while at rest. In SHM, it ensures objects attached or resting upon the moving system do not slip off due to movement. In the case of the carrot slice on the dinner plate, determining \(\mu_s\) helps ascertain the maximum oscillation speed before slipping. Calculated as 0.153 in our example, it tells us this is the ratio of the force needed to move the carrot slice to the weight of the carrot slice. This value was found using \(\mu_s = \frac{\omega^2 A}{g}\), emphasizing how fundamental it is to evaluate potential motion and safety in systems.
Angular Frequency
Angular frequency \(\omega\) is an essential component of SHM and represents how fast the object cycles through its motion, measured in radians per second. It's calculated through the relation \(\omega = \frac{v}{\sqrt{A^2 - x^2}}\). In the exercise, it was determined to be approximately 3.872 rad/s. This value underlines how rapidly the system oscillates around the equilibrium position. Angular frequency ties closely with period \(T\), as they provide a more profound insight into the dynamics of oscillation. Furthermore, angular frequency allows us to link linear properties, such as speed and acceleration, to the rotational concepts, facilitating a comprehensive analysis of SHM.

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Most popular questions from this chapter

An experimental package and its support structure, which are to be placed on board the International Space Station, act as an underdamped spring-mass system with a force constant of \(2.1 \times 10^{5} \mathrm{N} / \mathrm{m}\) and mass 108 \(\mathrm{kg}\) . A NASA requirement is that resonance for forced oscillations not occur for any frequency below 35 \(\mathrm{Hz}\) . Does this package meet the requirement?

You want to construct a pendulum with a period of 4.00 \(\mathrm{s}\) at a location where \(g=\) 9.80 \(\mathrm{m} / \mathrm{s}^{2} .\) (a) What is the length of a simple pendulum having this period? (b) Suppose the pendulum must be mounted in a case that is not more than 0.50 \(\mathrm{m}\) high. Can you devise a pendulum having a period of 4.00 s that will satisfy this requirement?

A \(40.0 .\) N force strethes a vertical spring 0.250 \(\mathrm{m}\) . (a) What mass must be suspended from the spring so that the system will oscillate with a period of 1.00 \(\mathrm{s} ?(6)\) If the amplitude of the motion is 0.050 \(\mathrm{m}\) and the period is that specified in part (a), where is the object and in what direction is it moving 0.35 \(\mathrm{s}\) after it has passed the equilibrium position, moving downward? (c) What force (magnitude and direction) does the spring exert on the object when it is 0.030 \(\mathrm{m}\) below the equilibrium position, moving upward?

Weighing Astronauts. This procedure has actually been used to "weigh" astronauts in space. A \(42.5-\mathrm{kg}\) chair is attached to a spring and allowed to oscillate. When it is empty, the chair takes 1.30 s to make one complete vibration. But with an astronaut sitting in it, with her feet off the floor, the chair takes 2.54 s for one cycle. What is the mass of the astronaut?

A mass \(m\) is attached to one end of a massess spring with a force constant \(k\) and an unstretched length \(l_{0}\) . The other end of the spring is free to turn about a nail driven into a frictionless, horizontal surface (Fig. 13.44\() .\) The mass is made to revolve in a circle with an angular frequency of revolution \(\omega^{\prime}\) , (a) Calculate the length \(l\) of the spring as a function of \(\omega^{\prime} .\) (b) What happens to the result in part (a) when \(\omega^{\prime}\) approaches the natural frequency \(\omega=\sqrt{k} / m\) of the mass-spring system? (ff your result bothers you, remember that massless springs and frictionless surfaces don't exist as such, but are only approximate descriptions of real springs and surfaces. Also, Hooke's law is only an approximation of the way real springs behave; the greater the elongation of the spring, the greater the deviation from Hooke's law.)

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