A bacterial culture starts with 200 cells and grows according to dN/dt = k·N with k = 0.02 h⁻¹. How many cells N are there after 24 h?
Differential equations worksheet with answers
1.Easy
N0 = 200k = 0.02 h⁻¹t = 24 h
N =
2.Easy
A mass–spring–damper is described by y″ + 19.2y′ + 64y = 0. Compare it with y″ + 2ζωny′ + ωn²y = 0 and find the damping ratio ζ.
y″ + 19.2y′ + 64y = 0
ζ =
3.Medium
Solve y″ + 6y′ + 8y = 0 with y(0) = 3 and y′(0) = 6. Find y(1).
y″ + 6y′ + 8y = 0y(0) = 3y′(0) = 6
y(1) =
4.Medium
Solve y″ + 5y′ + 4y = 0 with y(0) = 3 and y′(0) = 6. Find y(1).
y″ + 5y′ + 4y = 0y(0) = 3y′(0) = 6
y(1) =
5.Hard
A system obeys y″ + y′ + 4.25y = 42.5 for t ≥ 0, starting from rest: y(0) = 0, y′(0) = 0. Find the peak value ymax of its step response.
y″ + y′ + 4.25y = 42.5y(0) = 0y′(0) = 0
ymax =
6.Hard
A system obeys y″ + y′ + 4.25y = 21.25 for t ≥ 0, starting from rest: y(0) = 0, y′(0) = 0. Find the peak value ymax of its step response.
y″ + y′ + 4.25y = 21.25y(0) = 0y′(0) = 0
ymax =
Answer key
- 1. N = 323.2
- 2. ζ = 1.2
- 3. y(1) = 1.108
- 4. y(1) = 2.152
- 5. ymax = 14.56
- 6. ymax = 7.28
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