A mass–spring–damper is described by y″ + 1.6y′ + 4y = 0. Compare it with y″ + 2ζωny′ + ωn²y = 0 and find the damping ratio ζ.
Differential equations worksheet with answers
1.Easy
y″ + 1.6y′ + 4y = 0
ζ =
2.Easy
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.
y″ + 3y′ + 2y = 0
r =
3.Medium
Solve y″ + 6y′ + 9y = 0 with y(0) = 2 and y′(0) = 2. Find y(2).
y″ + 6y′ + 9y = 0y(0) = 2y′(0) = 2
y(2) =
4.Medium
A can of soda at 5 °C is taken out of the fridge into a room at 24 °C. After 15 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 10 °C?
T0 = 5 °CTa = 24 °CT(15) = 12 °CT = 10 °C
t = min
5.Hard
A system obeys y″ + 4y′ + 29y = 145 for t ≥ 0, starting from rest: y(0) = 0, y′(0) = 0. Find y(0.5); angles in radians.
y″ + 4y′ + 29y = 145y(0) = 0y′(0) = 0
y(0.5) =
6.Hard
Solve the initial value problem y′ + y/x = 5x for x > 0, with y(1) = 0. Find y(2).
y′ + y/x = 5xy(1) = 0
y(2) =
Answer key
- 1. ζ = 0.4
- 2. r = −1
- 3. y(2) = 0.04462
- 4. t = 9.968 min
- 5. y(0.5) = 6.033
- 6. y(2) = 5.833
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