For the equation y″ + 3y′ + 2y = 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
1.Easy
y″ + 3y′ + 2y = 0
r =
2.Easy
A mass–spring–damper is described by y″ + 7.2y′ + 36y = 0. Compare it with y″ + 2ζωny′ + ωn²y = 0 and find the damping ratio ζ.
y″ + 7.2y′ + 36y = 0
ζ =
3.Medium
A forged steel part at 400 °C is left to cool in a workshop at 28 °C. It follows Newton's law of cooling, dT/dt = −k·(T − Tₐ). With k = 0.04 min⁻¹, find its temperature T after 33 min.
T0 = 400 °CTa = 28 °Ck = 0.04 min⁻¹t = 33 min
T = °C
4.Medium
Solve y″ + 4y′ + 4y = 0 with y(0) = 5 and y′(0) = 2. Find y(2).
y″ + 4y′ + 4y = 0y(0) = 5y′(0) = 2
y(2) =
5.Hard
Solve the initial value problem y′ + y/x = 2x for x > 0, with y(1) = −2. Find y(2).
y′ + y/x = 2xy(1) = −2
y(2) =
6.Hard
Solve the initial value problem y′ + y/x = 4x2 for x > 0, with y(1) = 2. Find y(2).
y′ + y/x = 4x2y(1) = 2
y(2) =
Answer key
- 1. r = −1
- 2. ζ = 0.6
- 3. T = 127.4 °C
- 4. y(2) = 0.5312
- 5. y(2) = 1.333
- 6. y(2) = 8.5
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