A mass–spring–damper is described by y″ + 4y′ + 100y = 0. Compare it with y″ + 2ζωny′ + ωn²y = 0 and find the damping ratio ζ.
Differential equations worksheet with answers
1.Easy
y″ + 4y′ + 100y = 0
ζ =
2.Easy
For the equation y″ + 6y′ + 5y = 0, find the root r of the characteristic equation that is closest to zero. It sets how slowly the solution dies out.
y″ + 6y′ + 5y = 0
r =
3.Medium
Solve y″ + 8y′ + 16y = 0 with y(0) = 3 and y′(0) = 4. Find y(1.5).
y″ + 8y′ + 16y = 0y(0) = 3y′(0) = 4
y(1.5) =
4.Medium
A forged steel part at 360 °C is left to cool in a workshop at 29 °C. It follows Newton's law of cooling, dT/dt = −k·(T − Tₐ). With k = 0.01 min⁻¹, find its temperature T after 58 min.
T0 = 360 °CTa = 29 °Ck = 0.01 min⁻¹t = 58 min
T = °C
5.Hard
Solve the initial value problem y′ + 3y/x = 2x2 for x > 0, with y(1) = −3. Find y(2).
y′ + 3y/x = 2x2y(1) = −3
y(2) =
6.Hard
A system obeys y″ + 4y′ + 8y = 16 for t ≥ 0, starting from rest: y(0) = 0, y′(0) = 0. Find the peak value ymax of its step response.
y″ + 4y′ + 8y = 16y(0) = 0y′(0) = 0
ymax =
Answer key
- 1. ζ = 0.2
- 2. r = −1
- 3. y(1.5) = 0.06693
- 4. T = 214.3 °C
- 5. y(2) = 2.25
- 6. ymax = 2.086
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