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A mass \(m\) at the end of a spring oscillates with a frequency of 0.83 Hz. When an additional 780-g mass is added to \(m\), the frequency is 0.60 Hz. What is the value of \(m\)?

Short Answer

Expert verified
The value of \(m\) is 0.854 kg.

Step by step solution

01

Understand the relationship between frequency and mass

In a spring-mass system, the frequency of oscillation \(f\) is related to the mass \(m\) and the spring constant \(k\) by the equation \(f = \frac{1}{2\pi} \sqrt{\frac{k}{m}}\). We will use this to set up equations for the system before and after adding the additional mass.
02

Equation setup for initial and changed frequencies

For the initial mass, the frequency is 0.83 Hz:\[f_1 = \frac{1}{2\pi} \sqrt{\frac{k}{m}} = 0.83 \]For the mass with the additional 780 g (0.78 kg), the frequency becomes 0.60 Hz:\[f_2 = \frac{1}{2\pi} \sqrt{\frac{k}{m + 0.78}} = 0.60\]
03

Isolate variables by solving equations

Square both sides of each equation to eliminate the square roots:\[\frac{k}{m} = (2\pi \times 0.83)^2 \]\[\frac{k}{m + 0.78} = (2\pi \times 0.60)^2 \]
04

Express \(k\) in terms of \(m\) and equate

From the first equation, express \(k\) in terms of \(m\):\[k = m (2\pi \times 0.83)^2 \]From the second equation, express \(k\) in terms of \(m + 0.78\):\[k = (m + 0.78) (2\pi \times 0.60)^2 \]Since \(k\) is the same for both cases, set the right sides of these equations equal to each other:\[m (2\pi \times 0.83)^2 = (m + 0.78) (2\pi \times 0.60)^2\]
05

Solve for the mass \(m\)

Expand the equations on both sides:\[m \times 4\pi^2 \times 0.6889 = (m + 0.78) \times 4\pi^2 \times 0.36\]Cancel out \(4\pi^2\) from both sides:\[m \times 0.6889 = (m + 0.78) \times 0.36\]Distribute and solve for \(m\):\[ 0.6889m = 0.36m + 0.2808\]\[ 0.6889m - 0.36m = 0.2808\]\[ 0.3289m = 0.2808\]\[ m = \frac{0.2808}{0.3289} \]Calculate to find \(m\) approximately equal to 0.854 kg.

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Key Concepts

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

Oscillation Frequency
In a spring-mass system, the oscillation frequency is how quickly the mass moves back and forth on the spring. Generally, it's measured in hertz (Hz), which represents the number of oscillations per second. For our given problem, the mass initially oscillates with a frequency of 0.83 Hz.

The formula connecting frequency ( \( f \) ) with spring constant ( \( k \) ) and mass ( \( m \) ) is:
  • \( f = \frac{1}{2\pi} \sqrt{\frac{k}{m}} \)
This elegantly shows that frequency is inversely proportional to the square root of the mass. Basically, as the mass increases, the frequency decreases along a specific curve.

When an additional 780 g (or 0.78 kg) is added, the frequency reduces to 0.60 Hz. This behavior aligns with the inverse relationship between mass and frequency. In practice, this means heavier objects tend to oscillate slower since more force is needed to initiate and maintain their motion.
Spring Constant
The spring constant ( \( k \) ) is a critical factor in determining how "stiff" a spring is. It is measured in newtons per meter (N/m) and provides insight into the relationship between the force applied to the spring and how much it stretches or compresses.

Using the frequency formula, \( f = \frac{1}{2\pi} \sqrt{\frac{k}{m}} \), we can see \( k \) also influences the frequency. To solve problems like the one at hand, expressing \( k \) in terms of \( m \) through equation manipulation is vital. For example, as derived from the given frequencies, \( k \) can be expressed for different states of mass:
  • Initial: \( k = m (2\pi \times 0.83)^2 \)
  • With additional mass: \( k = (m + 0.78) (2\pi \times 0.60)^2 \)
Understanding that \( k \) remains constant allows for comparison and solving of these two equations for \( m \). This highlights \( k \)'s robustness—it doesn't change just because the mass or frequency does.
Equation Solving
Breaking down the task of solving for unknown variables is a key skill in physics. Solving equations requires a systematic approach, especially in dynamics problems like this one.

For our scenario, derive from the given mathematical equations, both describing the original and altered system frequencies:
  • First equation (for 0.83 Hz): \( \frac{k}{m} = (2\pi \times 0.83)^2 \)
  • Second equation (for 0.60 Hz): \( \frac{k}{m + 0.78} = (2\pi \times 0.60)^2 \)
By squaring both sides of each equation and solving for \( k \) , one can establish a relational equality. Since \( k \) is the same for both masses, the expressions for \( k \) in terms of \( m \) are set equal. This simplifies to a single equation: \( m (2\pi \times 0.83)^2 = (m + 0.78) (2\pi \times 0.60)^2 \) .

Finally, isolating \( m \) by doing some algebraic rearrangements gives \( m = \frac{0.2808}{0.3289} \) , solving to get \( m \approx 0.854 \) kg. Throughout, each step hinges on keeping equations balanced and isolating variables logically, reinforcing fundamental mathematical and physical principles.

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Most popular questions from this chapter

A 0.650-kg mass oscillates according to the equation \(x =\) 0.25 sin(4.70 \(t\)) where \(x\) is in meters and is in seconds. Determine (\(a\)) the amplitude, (\(b\)) the frequency, (\(c\)) the period, (\(d\)) the total energy, and (\(e\)) the kinetic energy and potential energy when \(x\) is 15 cm.

The intensity of an earthquake wave passing through the Earth is measured to be 3.0 \(\times 10^6\) J\(/m^2 \cdot \) s at a distance of 54 km from the source. (a) What was its intensity when it passed a point only 1.0 km from the source? (b) At what rate did energy pass through an area of 2.0 m\(^2\) at 1.0 km?

A bug on the surface of a pond is observed to move up and down a total vertical distance of 0.12 m, lowest to highest point, as a wave passes. (\(a\)) What is the amplitude of the wave? (\(b\)) If the amplitude increases to 0.16 m, by what factor does the bug's maximum kinetic energy change?

For any type of wave that reaches a boundary beyond which its speed is increased, there is a maximum incident angle if there is to be a transmitted refracted wave. This maximum incident angle \(\theta_{iM}\) corresponds to an angle of refraction equal to 90\(^\circ\). If \(\theta_i > \theta_{iM}\) , all the wave is reflected at the boundary and none is refracted, because refraction would correspond to sin \(\theta_r > 1\) (where \(\theta_r\) is the angle of refraction), which is impossible. This phenomenon is referred to as \(\textit{total internal reflection}\). (\(a\)) Find a formula \(\theta_{iM}\) for using the law of refraction, Eq. 11\(-\)20. (\(b\)) How far from the bank should a trout fisherman stand (Fig. 11\(-\)61) so trout won't be frightened by his voice (1.8 m above the ground)? The speed of sound is about 343 m\(/\)s in air and 1440 m\(/\)s in water.

An object of unknown mass \(m\) is hung from a vertical spring of unknown spring constant \(k\), and the object is observed to be at rest when the spring has stretched by 14 cm. The object is then given a slight push upward and executes SHM. Determine the period \(T\) of this oscillation.

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