A bacterial culture starts with 200 cells and grows according to dN/dt = k·N with k = 0.39 h⁻¹. How many cells N are there after 17 h?
Differential equations worksheet with answers
1.Easy
N0 = 200k = 0.39 h⁻¹t = 17 h
N =
2.Easy
For the equation y″ + 6y′ + 8y = 0, find the root r of the characteristic equation that is closest to zero. It sets how slowly the solution dies out.
y″ + 6y′ + 8y = 0
r =
3.Medium
Solve y″ + 5y′ + 6y = 0 with y(0) = 4 and y′(0) = -2. Find y(0.5).
y″ + 5y′ + 6y = 0y(0) = 4y′(0) = -2
y(0.5) =
4.Medium
Solve y″ + 8y′ + 16y = 0 with y(0) = 5 and y′(0) = -2. Find y(2).
y″ + 8y′ + 16y = 0y(0) = 5y′(0) = -2
y(2) =
5.Hard
Solve the initial value problem y′ + 2y/x = 6x for x > 0, with y(1) = 4. Find y(3).
y′ + 2y/x = 6xy(1) = 4
y(3) =
6.Hard
A system obeys y″ + 3y′ + 6.25y = 6.25 for t ≥ 0, starting from rest: y(0) = 0, y′(0) = 0. Find y(1.5); angles in radians.
y″ + 3y′ + 6.25y = 6.25y(0) = 0y′(0) = 0
y(1.5) =
Answer key
- 1. N = 151496
- 2. r = −2
- 3. y(0.5) = 2.34
- 4. y(2) = 0.01375
- 5. y(3) = 13.78
- 6. y(1.5) = 1.093
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