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This procedure has been used to "weigh" astronauts in space: A 42.5-kg chair is attached to a spring and allowed to oscillate. When it is empty, the chair takes 1.30 s to make one complete vibration. But with an astronaut sitting in it, with her feet off the floor, the chair takes 2.54 s for one cycle. What is the mass of the astronaut?

Short Answer

Expert verified
The mass of the astronaut is 69.3 kg.

Step by step solution

01

Understand the Problem

We are tasked with finding the mass of the astronaut by using the oscillation period of a spring-mass system. Given parameters include the mass of the chair and the periods of oscillation with and without the astronaut.
02

Use the Formula for Period of a Spring-Mass System

The formula to calculate the period (T) of a mass-spring system is:\[ T = 2\pi \sqrt{\frac{m}{k}} \]where \(m\)is the total mass and \(k\)is the spring constant.
03

Calculate the Spring Constant (k)

Using the period of the empty chair (T = 1.30 \, s)and chair mass (m = 42.5 \, kg): \[ 1.30 = 2\pi \sqrt{\frac{42.5}{k}} \]Solve for \(k\)by squaring both sides and rearranging: \[ k = \frac{4\pi^2 \times 42.5}{1.3^2} \]Calculate \(k\).
04

Calculate the Total Mass with Astronaut

With the astronaut, the period is2.54s:\[ 2.54 = 2\pi \sqrt{\frac{m_{total}}{k}} \]where\(m_{total}\)is the total mass (chair + astronaut). Solve for\(m_{total}\):\[ m_{total} = \frac{k \times 2.54^2}{4\pi^2} \]Substitute\(k\)from Step 3 and calculate\(m_{total}\).
05

Determine the Mass of the Astronaut

Now, subtract the mass of the chair from the total mass:\[ m_{astronaut} = m_{total} - 42.5 \]Solve for\(m_{astronaut}\).

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Key Concepts

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

Oscillation Period
The oscillation period is a key component in understanding how systems like a spring-mass setup function. In simple terms, the oscillation period is the time it takes for the system to complete one full cycle of movement.
In the given problem, there are two different oscillation periods:
  • A chair without the astronaut, which takes 1.30 seconds per cycle.
  • The same chair with the astronaut, where the period extends to 2.54 seconds per cycle.
These periods are crucial as they allow us to determine the mass of the astronaut using specific equations related to the spring-mass system. Longer oscillation periods indicate a greater total mass. This concept is directly applied to measure weight in environments like space, where scales don't function like they do on Earth.
Spring Constant
The spring constant, denoted as \(k\), is a measure of a spring's stiffness. This constant plays a significant role in determining how a spring-mass system behaves. The stiffer the spring, the larger the spring constant, meaning the spring exerts more force when stretched or compressed.
To find the spring constant in our exercise, we use the oscillation period of the empty chair. By rearranging the equation \( T = 2\pi \sqrt{\frac{m}{k}} \), and squaring both sides, we solve for \(k\):
  • Plug in the empty chair period (1.30 seconds) and chair mass (42.5 kg) into the formula.
  • Calculate \(k\) using the formula: \[ k = \frac{4\pi^2 \times 42.5}{1.3^2} \]
Once the spring constant is known, it helps in determining the total mass of the system (chair plus astronaut) by allowing us to relate changes in period to changes in mass.
Mass Calculation
Calculating the mass of an object in a spring-mass system involves using the known properties of the system, such as the spring constant and the oscillation periods.
For a system with a spring constant \(k\) and a period \(T\), the formula \( T = 2\pi \sqrt{\frac{m}{k}} \) can be rearranged to solve for the total mass \(m\):
  • The formula becomes: \[ m_{total} = \frac{k \times T^2}{4\pi^2} \]
  • Using the given period of the system with the astronaut (2.54 seconds), substitute into the formula to find \(m_{total}\): the mass of chair and astronaut combined.
Finally, to find the astronaut's mass, subtract the known mass of the chair (42.5 kg) from this total mass.
This calculation highlights how oscillation periods and spring constants shape our understanding of mass in these systems.
Astronaut Weight Measurement
Measuring an astronaut's weight in space is quite a challenge due to the absence of gravity as we know it on Earth. However, this problem can be cleverly solved using properties of oscillation and spring-mass systems.
The setup involves:
  • A chair attached to a spring, oscillating freely.
  • Measurement of periods when the chair is empty and when the astronaut is seated.
By comparing these two periods, we calculate the spring constant and deduce the total mass using the formulas mentioned earlier. The astronaut's mass is then simply derived by subtracting the mass of the chair.
This ingenious method allows astronauts' masses to be measured accurately, even in space where normal scales are ineffective. It shows how physics principles like oscillation and spring forces are applied creatively beyond the confines of Earth.

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