A mass–spring–damper is described by y″ + 9.6y′ + 36y = 0. Compare it with y″ + 2ζωny′ + ωn²y = 0 and find the damping ratio ζ.
Differential equations worksheet with answers
1.Easy
y″ + 9.6y′ + 36y = 0
ζ =
2.Easy
A quantity grows according to dy/dt = k·y with k > 0. It is 120 at t = 0 and 204 at t = 11 h. Find the rate constant k in h⁻¹.
y(0) = 120y(11) = 204
k = h⁻¹
3.Medium
Solve y″ + 6y′ + 9y = 0 with y(0) = 3 and y′(0) = 0. Find y(2).
y″ + 6y′ + 9y = 0y(0) = 3y′(0) = 0
y(2) =
4.Medium
Solve y″ + 2y′ + y = 0 with y(0) = 2 and y′(0) = -1. Find y(1).
y″ + 2y′ + y = 0y(0) = 2y′(0) = -1
y(1) =
5.Hard
Solve the initial value problem y′ + 2y/x = 4 for x > 0, with y(1) = −1. Find y(2).
y′ + 2y/x = 4y(1) = −1
y(2) =
6.Hard
A system obeys y″ + y′ + 9.25y = 9.25 for t ≥ 0, starting from rest: y(0) = 0, y′(0) = 0. Find y(0.25); angles in radians.
y″ + y′ + 9.25y = 9.25y(0) = 0y′(0) = 0
y(0.25) =
Answer key
- 1. ζ = 0.8
- 2. k = 0.04824 h⁻¹
- 3. y(2) = 0.05205
- 4. y(1) = 1.104
- 5. y(2) = 2.083
- 6. y(0.25) = 0.254
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