A mass–spring–damper is described by y″ + 0.8y′ + 4y = 0. Compare it with y″ + 2ζωny′ + ωn²y = 0 and find the damping ratio ζ.
Differential equations worksheet with answers
For the equation y″ + 7y′ + 12y = 0, find the root r of the characteristic equation that is closest to zero. It sets how slowly the solution dies out.
Solve y″ + 6y′ + 9y = 0 with y(0) = 2 and y′(0) = 0. Find y(2).
A can of soda at 6 °C is taken out of the fridge into a room at 26 °C. After 12 min its temperature is 14 °C. It follows Newton's law of cooling, dT/dt = −k·(T − Tₐ). How long after the start, t, does it take to reach 21 °C?
A system obeys y″ + 3y′ + 6.25y = 12.5 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″ + y′ + 25.25y = 50.5 for t ≥ 0, starting from rest: y(0) = 0, y′(0) = 0. Find the peak value ymax of its step response.
Answer key
- 1. ζ = 0.2
- 2. r = −3
- 3. y(2) = 0.0347
- 4. t = 32.57 min
- 5. ymax = 2.19
- 6. ymax = 3.461
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