Chapter 15: Problem 59
The balance wheel of an old-fashioned watch oscillates with angular amplitude \(\pi\) rad and period \(0.600 \mathrm{~s}\). Find (a) the maximum angular speed of the wheel, (b) the angular speed at displacement \(\pi / 2 \mathrm{rad}\), and (c) the magnitude of the angular acceleration at displacement \(\pi / 4 \mathrm{rad}\).
Short Answer
Step by step solution
Identify Given Values
Find the Angular Frequency
Calculate Maximum Angular Speed
Determine Angular Speed at \(\pi/2\) rad
Calculate Angular Acceleration at \(\pi/4\) rad
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Angular Amplitude
For the balance wheel of an old-fashioned watch, as given in our example, the angular amplitude is \( \pi \) radians. This indicates that the wheel can swing a total angle of \( \pi \) radians from one extreme end to the other.
- Importance: The angular amplitude is critical because it informs us about the range of motion of the system.
- Relation: It is a factor in determining the maximum angular speed, as it multiplies with angular frequency.
Angular Frequency
- Significance: Angular frequency is pivotal in calculating other parameters such as angular speed and acceleration.
- Role in Motion: It directly relates to how fast the cyclic motion repeats itself.
Maximum Angular Speed
It can be calculated using the formula \( \omega_{\text{max}} = \omega A \), where \( \omega \) is the angular frequency and \( A \) is the angular amplitude.From our example, we have \( \omega \approx 10.47 \) rad/s and \( A = \pi \) rad, resulting in a maximum angular speed of about 32.93 rad/s.
- Use: Knowing the maximum angular speed helps in designing components that can sustain the maximum kinetic load.
- Behavior Interpretation: It indicates the peak energy point during the oscillation cycle.
Angular Acceleration
It is represented by \( a \) and is calculated using \( a = -\omega^2 x \), where \( x \) is the displacement from equilibrium. In our problem, at a displacement of \( \pi/4 \) rad, the angular acceleration becomes approximately -86.25 rad/s².
- Magnitude: We often take the absolute value to understand its effect without considering direction, resulting in 86.25 rad/s².
- Application: Angular acceleration information helps in understanding how forces within the system change over time.