What is the period of a simple pendulum that is \(1.00 \mathrm{~m}\) long in each situation? a) in the physics lab b) in an clevator accelerating at \(2.10 \mathrm{~m} / \mathrm{s}^{2}\) upward c) in an elevator accelerating \(2.10 \mathrm{~m} / \mathrm{s}^{2}\) downward d) in an elevator that is in free fall

Short Answer

Expert verified
Answer: The period of the simple pendulum is: a) Approximately 2.00 s in the physics lab b) Approximately 1.82 s in an elevator accelerating upward c) Approximately 2.26 s in an elevator accelerating downward d) Undefined in an elevator in free fall

Step by step solution

01

Calculate the period in normal conditions (physics lab)

To find the period of the pendulum in the physics lab, we'll use the formula \(T=2\pi\sqrt{\frac{l}{g}}\), where \(l\) is the length of the pendulum and \(g\) is the standard gravitational acceleration (\(9.81 \mathrm{~m} / \mathrm{s}^{2}\)). Given that the length of the pendulum is \(1.00 \mathrm{~m}\), we can plug the values into the formula to find the period. T = 2π × √(1.00 m / 9.81 m/s²) ≈ 2.00 s
02

Calculate the period in an elevator accelerating upward

When the elevator is accelerating upward, the effective gravitational acceleration is the sum of the normal gravitational acceleration and the acceleration of the elevator. In this case, \(g'=g+a\), where \(a = 2.10 \mathrm{~m} / \mathrm{s}^{2}\). We can then use the formula again to find the period. g' = 9.81 m/s² + 2.10 m/s² = 11.91 m/s² T = 2π × √(1.00 m / 11.91 m/s²) ≈ 1.82 s
03

Calculate the period in an elevator accelerating downward

When the elevator is accelerating downward, the effective gravitational acceleration is the difference between the normal gravitational acceleration and the acceleration of the elevator. In this case, \(g'=g-a\), where \(a = 2.10 \mathrm{~m} / \mathrm{s}^{2}\). We can then use the formula again to find the period. g' = 9.81 m/s² - 2.10 m/s² = 7.71 m/s² T = 2π × √(1.00 m / 7.71 m/s²) ≈ 2.26 s
04

Calculate the period in an elevator in free fall

When the elevator is in free fall, the effective gravitational acceleration is 0 m/s² (since the acceleration due to gravity is canceled by the acceleration of the elevator). Since the denominator of the formula would be 0, the period of the pendulum would be undefined (meaning the pendulum would not oscillate back and forth). In summary, the period of the simple pendulum is: a) \( T \approx 2.00 \mathrm{~s}\) in the physics lab b) \( T \approx 1.82 \mathrm{~s}\) in an elevator accelerating upward c) \( T \approx 2.26 \mathrm{~s}\) in an elevator accelerating downward d) Undefined in an elevator in free fall

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Key Concepts

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

Gravitational Acceleration
Understanding gravitational acceleration is essential when studying the motion of a simple pendulum. Gravitational acceleration, denoted as \( g \), is the acceleration imparted to objects due to the force of gravity exerted by a massive body, such as Earth. On the surface of the Earth, this value is approximately \( 9.81 \text{m/s}^2 \), though it can vary slightly depending on location.

When dealing with pendulum motion, gravitational acceleration is a crucial part of the formula to calculate the period, which is the duration of one complete cycle of movement. The formula for the period \( T \) of a simple pendulum is \( T = 2\text{π} \times \text{√}\frac{l}{g} \), where \( l \) represents the length of the pendulum. As gravitational acceleration increases, the period decreases, meaning the pendulum swings more quickly. If \( g \) decreases, the period increases and the pendulum swings more slowly.

Thus, gravitational acceleration sets the pace at which the pendulum oscillates when other factors remain constant. Having a strong grasp on how \( g \) influences the pendulum's period is fundamental to understanding pendulum dynamics in different scenarios.
Effective Gravitational Acceleration
In scenarios where the gravitational conditions are altered, such as inside an accelerating elevator, we introduce the concept of effective gravitational acceleration, denoted by \( g' \). It expresses the combined effects of Earth's gravity and other accelerations acting upon a system.

For example, when a simple pendulum is in an elevator accelerating upward, the acceleration of the elevator \( a \) adds to Earth’s gravitational pull, yielding \( g' = g + a \). Conversely, if the elevator accelerates downward, the effective gravitational acceleration becomes \( g' = g - a \), since the elevator's acceleration works against Earth's gravity. It's important to note that these conditions alter how the pendulum swings, affecting the period accordingly.

Interestingly, if an elevator were in free fall, the acceleration would negate gravity’s effect completely, leading to \( g' = 0 \), and the pendulum would experience weightlessness, resulting in no oscillation. This effectively demonstrates the significance of effective gravitational acceleration in altered environments and is a critical concept for students to understand when considering the motion of pendulums in non-standard conditions.
Pendulum Oscillation
Pendulum oscillation refers to the regular, repetitive movement of a pendulum swinging back and forth under the influence of gravity. Each swing from its starting position to the opposite side and back is considered one complete oscillation. A key feature of pendulum motion is that it follows a regular time period, if not acted upon by external forces.

The time it takes to complete one full oscillation is referred to as the period, which we’ve seen can be calculated using the length of the pendulum and the gravitational acceleration acting upon it. Factors that affect pendulum oscillation include the length of the pendulum and the strength of gravity, but not the mass of the pendulum or the amplitude of the swing, as long as the amplitudes are small. This assumption is recognized in the context of the simple harmonic motion that pendulums exhibit, where the restoring force is directly proportional to the displacement.

Understanding the intricacies of pendulum oscillation not only deepens knowledge in physics regarding periodic motion but also paves the way for comprehending more complex systems influenced by a range of forces and accelerations.

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Most popular questions from this chapter

A small mass, \(m=50.0 \mathrm{~g}\), is attached to the end of a massless rod that is hanging from the ceiling and is free to swing. The rod has length \(L=1.00 \mathrm{~m} .\) The rod is displaced \(10.0^{\circ}\) from the vertical and released at time \(t=0\). Neglect air resistance. What is the period of the rod's oscillation? Now suppose the entire system is immersed in a fluid with a small damping constant, \(b=0.0100 \mathrm{~kg} / \mathrm{s},\) and the rod is again released from an initial displacement angle of \(10.0^{\circ}\). What is the time for the amplitude of the oscillation to reduce to \(5.00^{\circ}\) ? Assume that the damping is small Also note that since the amplitude of the oscillation is small and all the mass of the pendulum is at the end of the rod, the motion of the mass can be treated as strictly linear, and you can use the substitution \(R \theta(t)=x(t),\) where \(R=1.0 \mathrm{~m}\) is the length of the pendulum rod.

14.10 A pendulum is suspended from the ceiling of an elevator. When the elevator is at rest, the period of the pendulum is \(T\). The elevator accelerates upward, and the period of the pendulum is then a) still T. b) less than \(T_{-}\) c) greater than \(T\).

A mass \(M=0.460 \mathrm{~kg}\) moves with an initial speed \(v=3.20 \mathrm{~m} / \mathrm{s}\) on a level frictionless air track. The mass is initially a distance \(D=0.250 \mathrm{~m}\) away from a spring with \(k=\) \(840 \mathrm{~N} / \mathrm{m}\), which is mounted rigidly at one end of the air track. The mass compresses the spring a maximum distance \(d\), before reversing direction. After bouncing off the spring the mass travels with the same speed \(v\), but in the opposite dircction. a) Determine the maximum distance that the spring is compressed. b) Find the total elapsed time until the mass returns to its starting point. (Hint: The mass undergoes a partial cycle of simple harmonic motion while in contact with the spring.)

14.3 A mass that can oscillate without friction on a horizontal surface is attached to a horizontal spring that is pulled to the right \(10.0 \mathrm{~cm}\) and is released from rest. The period of oscillation for the mass is \(5.60 \mathrm{~s}\). What is the speed of the mass at \(t=2.50 \mathrm{~s} ?\) a) \(-2.61 \cdot 10^{-1} \mathrm{~m} / \mathrm{s}\) b) \(-3.71 \cdot 10^{-2} \mathrm{~m} / \mathrm{s}\) c) \(-3.71 \cdot 10^{-1} \mathrm{~m} / \mathrm{s}\) d) \(-2.01 \cdot 10^{-1} \mathrm{~m} / \mathrm{s}\)

Consider two identical oscillators, each with spring constant \(k\) and mass \(m\), in simple harmonic motion. One oscillator is started with initial conditions \(x_{0}\) and \(v_{j}\) the other starts with slightly different conditions, \(x_{0}+\delta x\) and \(v_{0}+\delta v_{1}\) a) Find the difference in the oscillators' positions, \(x_{1}(t)-x_{2}(t)\) for all t. b) This difference is bounded; that is, there exists a constant \(C\) independent of time, for which \(\left|x_{1}(t)-x_{2}(t)\right| \leq C\) holds for all \(t\). Find an expression for \(C\). What is the best bound, that is, the smallest value of \(C\) that works? (Note: An important characteristic of chaotic systems is exponential sensitivity to initial conditions; the difference in position of two such systems with slightly different initial conditions grows exponentially with time. You have just shown that an oscillator in simple harmonic motion is not a chaotic system.)

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