A mass–spring–damper is described by y″ + 2.4y′ + 16y = 0. Compare it with y″ + 2ζωny′ + ωn²y = 0 and find the damping ratio ζ.
Differential equations worksheet with answers
For the equation y″ + 5y′ + 4y = 0, find the root r of the characteristic equation that is closest to zero. It sets how slowly the solution dies out.
Solve y″ + 3y′ + 2y = 0 with y(0) = 1 and y′(0) = -4. Find y(1).
A can of soda at 6 °C is taken out of the fridge into a room at 28 °C. After 7 min its temperature is 12 °C. It follows Newton's law of cooling, dT/dt = −k·(T − Tₐ). How long after the start, t, does it take to reach 8 °C?
A tank holds 500 L of water in which 10 kg of salt is dissolved. Brine with 0.05 kg of salt per litre flows in at 2 L/min, and the well-mixed solution flows out at the same rate. How much salt m is in the tank after 10 min?
Solve y′ + 3y = 10e−t with y(0) = 0. Find y(2).
Answer key
- 1. ζ = 0.3
- 2. r = −1
- 3. y(1) = −0.3298
- 4. t = 2.095 min
- 5. m = 10.59 kg
- 6. y(2) = 0.6643
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