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A mass on a string of unknown length oscillates as a pendulum with a period of 4.0 s. What is the period if a. The mass is doubled? b. The string length is doubled? c. The string length is halved? Parts a to d are independent questions, each referring to the initial situation.

Short Answer

Expert verified
If the mass is doubled, the period remains the same, i.e., 4.0s. If the string length is doubled, the new period is approximately 5.66s. If the string length is halved, the new period is approximately 2.83s.

Step by step solution

01

Evaluate the effect of the mass on the period

The period \(T\) of a pendulum does not depend on its mass according to the formula \(T = 2\pi \sqrt{{L}/{g}}\). Therefore, even if the mass of the pendulum is doubled, the period will remain the same.
02

Evaluate the effect of doubling the string length on the period

Doubling the length of the string (from \(L\) to \(2L\)) would change the period according to the formula \(T = 2\pi \sqrt{{L}/{g}}\). We know that the square root function is not linear, but we can simplify to see that the new period \(T_{2L}\) would be \(T_{2L} = 2\pi \sqrt{{2L}/{g}} = \sqrt{2}T\). Thus, the new period would be \(T_{2L} = \sqrt{2}\times 4.0s\). Calculate the exact value.
03

Evaluate the effect of halving the string length on the period

Halving the length of the string (from \(L\) to \(L/2\)) would change the period according to the formula \(T = 2\pi \sqrt{{L}/{g}}\). Therefore the new period \(T_{L/2}\) would be \(T_{L/2} = 2\pi \sqrt{{L/2}/{g}} = \frac{T}{\sqrt{2}}\). Thus, the new period would be \(T_{L/2} = \frac{4.0s}{\sqrt{2}}\). Calculate the exact value.

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Key Concepts

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

Oscillation
Oscilation is a repetitive variation, typically in time, of some measure. In the context of a pendulum, it refers to the to-and-fro movement a pendulum exhibits as it swings. This movement, governed by gravity and the length of its supporting string, repeats in cycles known as periods. Each period is one complete cycle from one extreme end to the other and back again.
In a simple pendulum, the oscillatory motion can be described as harmonic, meaning it follows a regular and predictable path. These oscillations are affected by several factors, most importantly the length of the string and the constant force of gravity. Therefore, understanding the oscillation of a pendulum helps us grasp how pendulums keep time, which is vital in many applications, from clocks to measuring the gravitational acceleration.
Pendulum Formula
The period of a pendulum, denoted as \(T\), can be calculated using the formula:
  • \(T = 2\pi \sqrt{\frac{L}{g}}\)
Here, \(L\) stands for the length of the pendulum's string, and \(g\) is the acceleration due to gravity, approximately 9.81 m/s² on Earth. This formula beautifully illustrates that for a simple pendulum, the time it takes to complete one oscillation—its period—depends only on these two factors.Importantly, in the formula, the period is independent of the mass of the pendulum. This might be counterintuitive as one might think heavier objects swing differently. However, the period is affected solely by the string length and gravitational pull, providing us with a straightforward and predictable way to calculate the pendulum's oscillation time.
Effect of Mass on Period
One intriguing aspect of pendulums is that their period remains constant regardless of the mass attached at the end. This is counter to what one might intuitively expect, as many physical processes are affected by the mass of the objects involved.By observing the formula \(T = 2\pi \sqrt{\frac{L}{g}}\), you can notice that mass doesn't appear. This means that, unlike other systems, a pendulum's period doesn't change if you were to attach more weight to it. Therefore, doubling or even halving the mass has no impact on how much time the pendulum takes to complete one full oscillation cycle.This property makes pendulums ideal for timekeeping, as changes in the mass due to loading or unloading do not affect their accuracy and repeatability in measuring time.
Effect of String Length on Period
The length of the string directly influences the period of a pendulum due to its presence in the pendulum formula \(T = 2\pi \sqrt{\frac{L}{g}}\). When you adjust the string length, the period alters according to the square root of that length.
  • Doubling the string length increases the period by a factor of \(\sqrt{2}\).
  • Conversely, halving the string length decreases the period by a factor of \(\sqrt{2}\).
This relationship means if you make the pendulum longer, it swings more slowly, taking longer to complete one cycle. On the other hand, a shorter pendulum swings more quickly, reducing its period.These changes are particularly important in practical applications, such as adjusting the timekeeping accuracy of pendulum clocks or tuning instruments that rely on pendulum mechanisms. Understanding and applying the effect of string length on the pendulum period allows for precise control over oscillation cycles.

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Most popular questions from this chapter

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