For the equation y″ + 6y′ + 8y = 0, find the root r of the characteristic equation that is closest to zero. It sets how slowly the solution dies out.
Differential equations worksheet with answers
A mass–spring–damper is described by y″ + 0.8y′ + 16y = 0. Compare it with y″ + 2ζωny′ + ωn²y = 0 and find the damping ratio ζ.
A can of soda at 4 °C is taken out of the fridge into a room at 26 °C. After 22 min its temperature is 22 °C. It follows Newton's law of cooling, dT/dt = −k·(T − Tₐ). How long after the start, t, does it take to reach 9 °C?
A cup of coffee at 95 °C is left in a room at 22 °C. After 24 min its temperature is 50 °C. It follows Newton's law of cooling, dT/dt = −k·(T − Tₐ). How long after the start, t, does it take to reach 73 °C?
A system obeys y″ + 4y′ + 29y = 58 for t ≥ 0, starting from rest: y(0) = 0, y′(0) = 0. Find the peak value ymax of its step response.
Solve y″ + 3y′ + 18.25y = 0 with y(0) = 2 and y′(0) = 0 (released from rest). Find y(1); angles in radians.
Answer key
- 1. r = −2
- 2. ζ = 0.1
- 3. t = 3.327 min
- 4. t = 8.982 min
- 5. ymax = 2.569
- 6. y(1) = −0.4183
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