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A 1/4-kg mass is attached to a spring with stiffness k=16 N/m. The mass is displaced 2 meters to the left of the equilibrium point and is released with no velocity. Suppose the system is undamped and unforced. Find the equation of motion of the mass. (14.) A 1-kg mass is attached to a spring with stiffness k=16 N/m. The mass is displaced 5 meters to the right of the equilibrium point and is released with no velocity. Suppose the damping is b=4 and the system is unforced. Find the equation of motion of the mass. (15.) A 1/2−kg mass is attached to a spring with stiffness k=10 N/m. The mass is displaced 1/2 meter to the left of the equilibrium point and is released with a rightward velocity of 2 m/s. Suppose the damping is b=4 and the system is unforced. Find the equation of motion of the mass.

User Dufaux
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Final answer:

The equation of motion for a mass attached to a spring can be derived using the second-order differential equation that represents simple harmonic motion, with specific solutions for undamped and damped motions. For undamped systems, the general solution is a cosine function with an amplitude, angular frequency, and phase shift. Damped systems require additional consideration of the damping factor to determine the equation of motion.

Step-by-step explanation:

To find the equation of motion for a mass attached to a spring, we use the second-order differential equation that represents the simple harmonic motion (SHM) of a mass-spring system:



m\(\frac{d^2x}{dt^2}\) + b\(\frac{dx}{dt}\) + kx = 0



In this case:

  • m is the mass of the object,
  • k is the spring constant,
  • x is the displacement from the equilibrium position,
  • b is the damping coefficient, and
  • \(\frac{dx}{dt}\) is the velocity of the object.



For an undamped and unforced system (b=0), the general solution is:



x(t) = Acos(\(\sqrt{\frac{k}{m}}\)t + \(\phi\))



For a damped and unforced system, the equation of motion depends on the nature of the damping:

  • Underdamped: \(\sqrt{k/m} > b/2m\),
  • Critically damped: \(\sqrt{k/m} = b/2m\),
  • Overdamped: \(\sqrt{k/m} < b/2m\).



If the system is underdamped, the equation of motion is:



x(t) = Ae^{(-b/2m)t}cos(\(\sqrt{\frac{k}{m} - \frac{b^2}{4m^2}}\)t + \(\phi\))



Using the given values for each scenario, apply the relevant formula to find the equations of motion. The amplitude (A), angular frequency (\(\sqrt{k/m}\)), damping factor (b/2m), and phase angle (\(\phi\)) will be determined based on the initial conditions such as displacement and velocity at t=0.

User Anthony Kung
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