Chapter 15: Problem 45
A performer seated on a trapeze is swinging back and forth with a period of \(8.85 \mathrm{~s}\). If she stands up, thus raising the center of mass of the trapeze \(+\) performer system by \(35.0 \mathrm{~cm}\), what will be the new period of the system? Treat trapeze \(+\) performer as a simple pendulum.
Short Answer
Step by step solution
Understanding the Problem
Recall the Formula for the Pendulum Period
Determine the Original Length of the Pendulum
Calculate the New Length
Calculate the New Period
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Period of Pendulum
The formula for the period of a simple pendulum is: \[T = 2\pi \sqrt{\frac{L}{g}}\]where:
- \(T\) is the period of the pendulum (in seconds),
- \(L\) is the length from the pivot to the center of mass (in meters),
- \(g\) is the acceleration due to gravity (approximately \(9.81 \, \mathrm{m/s^2}\) on Earth).
Center of Mass
When the performer stands up, they raise their personal center of mass, which in turn reduces the distance between the center of mass and the pivot. This change is essential because:
- It results in a shorter pendulum length,
- Creates a faster oscillation period.
Pendulum Length
Longer pendulums have longer periods, meaning they take more time to complete one full swing. In contrast, shorter pendulums swing faster. Mathematically, this is captured by the square root relationship in the pendulum period formula. In our exercise, initially, the pendulum length was approximately \(19.38\,\mathrm{m}\). By standing and raising the center of mass, the performer changed this length to approximately \(19.03\,\mathrm{m}\). The shorter a pendulum, the quicker it swings back and forth, reducing the period slightly from \(8.85\,\mathrm{s}\) to about \(8.80\,\mathrm{s}\).
The understanding of how pendulum length affects the period is beneficial not only in physics but also in practical applications like designing clocks and instruments that rely on pendulum mechanics.
Gravity
On Earth, gravity is approximately \(9.81\,\mathrm{m/s^2}\). This consistent gravitational acceleration allows us to predict pendulum behavior accurately using our known formulas. The period of a pendulum is directly related to the square root of the length divided by gravity. This means that on different planets with different gravitational forces, the pendulum's period would change accordingly.
This concept is crucial for understanding the fundamental principles of motion under Earth’s conditions, making it indispensable for education and various scientific fields. When flying to other planets or significantly changing altitude, scientists must account for variations in gravity, leading to differences in system behaviors like pendulum motion.