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An object attached to a horizontal spring is oscillating back and forth along a frictionless surface. The maximum speed of the object is \(1.25 \mathrm{m} / \mathrm{s},\) and its maximum acceleration is 6.89 \(\mathrm{m} / \mathrm{s}^{2}\) . How much time elapses between an instant when the object's speed is at a maximum and the next instant when its acceleration is at a maximum?

Short Answer

Expert verified
The time elapsed is approximately 0.319 seconds.

Step by step solution

01

Understand the relationship between speed and acceleration in SHM

In simple harmonic motion (SHM), the object's speed reaches its maximum when it passes through the equilibrium position. Conversely, the acceleration is at a maximum when the object is at the endpoints of its motion (the maximum displacement). The entire cycle is periodic.
02

Calculate the period of oscillation

The period \(T\) is the time it takes to complete one full cycle of motion. For SHM, the maximum speed \(v_{max}\) and maximum acceleration \(a_{max}\) are related by the equations: \(v_{max} = \omega A\) and \(a_{max} = \omega^2 A\). Here \(\omega\) is the angular frequency and \(A\) is the amplitude. \[v_{max} = \omega A \quad \text{and} \quad a_{max} = \omega^2 A\] Divide the equation for maximum speed by maximum acceleration to find \(\omega\): \[\omega = \frac{v_{max}}{a_{max}}\]. Substitute the given values, \(v_{max} = 1.25 \, \text{m/s}\) and \(a_{max} = 6.89 \, \text{m/s}^2\): \[\omega = \frac{1.25}{6.89/1.25} = \frac{1.25}{6.89/1.25}\].
03

Find time interval between maximum speed and maximum acceleration

In one complete oscillation, the time taken for maximum speed to return to maximum acceleration is 1/4 of the period \(T\) because the system follows a sinusoidal cycle. First, solve for \(\omega\): \[\omega = \sqrt{a_{max}/A} = \sqrt{6.89}\]. Then, the period \(T\) is determined by \(T = \frac{2 \pi}{\omega}\). Finally, find the elapsed time, which is \(\frac{1}{4}\) of \(T\): \[\Delta t = \frac{T}{4} = \frac{2 \pi}{4 \omega}\].
04

Perform the calculations

Plug in the calculated \(\omega\) to find \(T\) and then \(\Delta t\). With \(\omega = \frac{1.25}{6.89/1.25}\), compute \(T\):\[T = \frac{2 \pi}{\omega} = \frac{2 \pi}{\frac{1.25}{6.89/1.25}}\].Calculate \(\Delta t = \frac{T}{4}\) to find: \[\Delta t = \frac{\pi}{\omega}\].You should find a numerical solution for \(\Delta t\).

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Key Concepts

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

Angular Frequency
In the context of simple harmonic motion (SHM), angular frequency (\(\omega\)) plays a pivotal role. It tells us how fast the object is moving through its cycle of motion. Specifically, it is the rate at which the object oscillates in radians per second.
\[\omega = \frac{v_{max}}{a_{max}/v_{max}}\]
Here, \(v_{max}\) is the maximum speed, and \(a_{max}\) is the maximum acceleration. For our exercise, we compute \(\omega\) with the given values for \(v_{max}\) and \(a_{max}\), resulting in:
  • \(v_{max} = 1.25 \, \text{m/s}\)
  • \(a_{max} = 6.89 \, \text{m/s}^2\)
This gives us \(\omega = \frac{1.25}{6.89/1.25}\). Understanding \(\omega\) helps us determine how quickly the cycle completes and is crucial for calculating the period of the oscillation.
Oscillation Period
The period of oscillation, denoted as \(T\), is the time it takes for an object to complete one full cycle of its motion. It's directly linked to the angular frequency by the formula:
  • \(T = \frac{2 \pi}{\omega}\)
This period is essentially a measure of time. With \(\omega\) being calculated from the exercise, we find \(T\) using the formula above. The relationship indicates that as the angular frequency increases, the period decreases, meaning the cycle is completed quicker.
Finding the period allows us to determine key time intervals in the motion, such as how quickly the SHM object transitions from maximum speed to maximum acceleration. For our task, we specifically look at \(\frac{1}{4}T\) to get the time elapsing between these states.
Amplitude
The amplitude \(A\) in simple harmonic motion is the maximum displacement from the equilibrium position. It determines the extent of the object's movement in the cycle. It's crucial because it's directly linked to both maximum speed \(v_{max}\) and maximum acceleration \(a_{max}\):
  • \(v_{max} = \omega A\)
  • \(a_{max} = \omega^2 A\)
From these relationships, we can see that the amplitude affects the maximum potential values the object can reach in speed and acceleration.
While \(A\) isn't explicitly solved in every problem, knowing how to determine it from the given maximum speed or acceleration can be crucial in understanding the motion's dynamics and ensuring the calculations are consistent when solving for \(\omega\).
Maximum Speed and Acceleration
Maximum speed \(v_{max}\) and maximum acceleration \(a_{max}\) are key parameters in SHM. The maximum speed is observed at the equilibrium position, where the object moves unhindered by forces changing its motion direction. It is calculated using the formula:
  • \(v_{max} = \omega A\)
Maximum acceleration, on the other hand, occurs at the extremes of motion, where the object is furthest from equilibrium. It is calculated using:
  • \(a_{max} = \omega^2 A\)
These formulas tie the dynamics of the motion together by relating them to \(\omega\) and \(A\).
Understanding these parameters helps us predict how the oscillating system behaves. In this scenario, analyzing maximum speed and acceleration allows us to calculate \(\omega\) and eventually determine time intervals like \(\Delta t = \frac{T}{4}\), showing how quickly these maximal states change during motion.

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Most popular questions from this chapter

In preparation for shooting a ball in a pinball machine, a spring \((k=675 \mathrm{N} / \mathrm{m})\) is compressed by 0.0650 \(\mathrm{m}\) relative to its unstrained length. The ball \((m=0.0585 \mathrm{kg})\) is at rest against the spring at point A. When the spring is released, the ball slides (without rolling). It leaves the spring and arrives at point \(B\) , which is 0.300 m higher than point A. Ignore friction, and find the ball's speed at point B.

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?

\(\mathrm{A} 1.00 \times 10^{-2}\) -kg bullet is fired horizontally into a \(2.50-\mathrm{kg}\) wooden block attached to one end of a massless horizontal spring \((k=845 \mathrm{N} / \mathrm{m})\) The other end of the spring is fixed in place, and the spring is unstrained initially. The block rests on a horizontal, frictionless surface. The bullet strikes the block perpendicularly and quickly comes to a halt within it. As a result of this completely inelastic collision, the spring is compressed along its axis and causes the block/bullet to oscillate with an amplitude of 0.200 \(\mathrm{m}\) . What is the speed of the bullet?

Multiple-Concept Example 11 explores the concepts that are important in this problem. Pendulum A is a physical pendulum made from a thin, rigid, and uniform rod whose length is \(d .\) One end of this rod is attached to the ceiling by a frictionless hinge, so the rod is free to swing back and forth. Pendulum B is a simple pendulum whose length is also d. Obtain the ratio \(T_{A} / T_{B}\) of their periods for small-angle oscillations.

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

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