A mass–spring–damper is described by y″ + 3y′ + 25y = 0. Compare it with y″ + 2ζωny′ + ωn²y = 0 and find the damping ratio ζ.
Differential equations worksheet with answers
For the equation y″ + 8y′ + 15y = 0, find the root r of the characteristic equation that is closest to zero. It sets how slowly the solution dies out.
A forged steel part at 340 °C is left to cool in a workshop at 21 °C. It follows Newton's law of cooling, dT/dt = −k·(T − Tₐ). With k = 0.05 min⁻¹, find its temperature T after 37 min.
A forged steel part at 380 °C is left to cool in a workshop at 28 °C. After 48 min its temperature is 80 °C. It follows Newton's law of cooling, dT/dt = −k·(T − Tₐ). Find the constant k in min⁻¹.
A system obeys y″ + 2y′ + 17y = 170 for t ≥ 0, starting from rest: y(0) = 0, y′(0) = 0. Find the peak value ymax of its step response.
A system obeys y″ + 2y′ + 17y = 34 for t ≥ 0, starting from rest: y(0) = 0, y′(0) = 0. Find y(0.5); angles in radians.
Answer key
- 1. ζ = 0.3
- 2. r = −3
- 3. T = 71.16 °C
- 4. k = 0.03984 min⁻¹
- 5. ymax = 14.56
- 6. y(0.5) = 2.229
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