Applications of Higher-Order DEs - Examples & Applications

Spring-Mass Systems

Simple Harmonic Motion Problem (Free Undamped)

A mass of 2 kg is attached to a spring, stretching it by 0.98 m. The mass is released from rest at a position 0.1 m below the equilibrium position. Find the equation of motion x(t)x(t). Assume g=9.8 m/s2g = 9.8 \text{ m/s}^2.

Simple Harmonic Motion Solution

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Damped Spring-Mass Problem (Free Damped)

A 1 kg mass is attached to a spring with stiffness k=5k = 5 N/m. The system is immersed in a medium that offers a damping force equal to 2 times the instantaneous velocity. The mass is initially displaced 1 meter below equilibrium and released with an upward velocity of 2 m/s. Find the equation of motion.

Damped Spring-Mass Solution

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Forced Motion and Resonance

An undamped spring-mass system with m=1m=1 and k=9k=9 is driven by an external force F(t)=12sin(3t)F(t) = 12\sin(3t). If the system starts from rest at equilibrium (x(0)=0,x(0)=0x(0)=0, x'(0)=0), find the equation of motion and identify the phenomenon occurring.

Forced Motion Solution

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The Simple Pendulum

Simple Pendulum (Linearized)

A pendulum of length L=2.45L = 2.45 meters is displaced by a small angle of θ=0.1\theta = 0.1 radians and released from rest. Find the equation for the angle θ(t)\theta(t) over time. Use g=9.8 m/s2g = 9.8 \text{ m/s}^2.

Simple Pendulum Solution

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RLC Circuits

RLC Circuit Problem (Critically Damped)

An RLC circuit has L=1L=1 H, R=6R=6 Ω\Omega, C=1/9C=1/9 F, and E(t)=0E(t)=0. The initial charge on the capacitor is q(0)=1q(0)=1 C, and the initial current is i(0)=0i(0)=0 A. Find the charge q(t)q(t).

RLC Circuit Solution

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RLC Circuit Problem (Underdamped)

An RLC circuit has L=0.5L=0.5 H, R=2R=2 Ω\Omega, C=0.1C=0.1 F, and E(t)=0E(t)=0. q(0)=2q(0)=2 C, i(0)=0i(0)=0 A. Find q(t)q(t).

Underdamped RLC Solution

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Beam Deflection

Beam Deflection Problem (Cantilever)

A cantilever beam of length LL (fixed at x=0x=0, free at x=Lx=L) carries a constant distributed load w0w_0. Find the deflection curve y(x)y(x). The governing equation is EIy(4)=w0EI y^{(4)} = w_0.

Beam Deflection Solution

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Beam Deflection Problem (Simply Supported)

A simply supported beam of length LL (pinned at x=0x=0 and x=Lx=L) has a constant load w0w_0. Find y(x)y(x).

Simply Supported Beam Solution

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