(adsbygoogle = window.adsbygoogle || []).push({}); 1. The problem statement, all variables and given/known data

A brick of mass 6 kg hangs from the end of a spring. When the brick is at rest, the spring is stretched by 3 cm. The spring is then stretched an additional 4 cm and released. Assume there is no air resistance. Note that the acceleration due to gravity, g, is g=980 cm/s2.

Set up a differential equation with initial conditions describing the motion and solve it for the displacement s(t) of the mass from its equilibrium position (with the spring stretched 3 cm).

2. Relevant equations

my'' + by' + ky = F_{external}

y(0) = y_{0}+ initial displacement

y'(0) = V_{0}

m = mass

b = damping constant

k = spring constant

F = -kx

3. The attempt at a solution

I get:

k = 19.6N/cm

y(0) = -4cm

y'(0) = 0

I'm assuming b = 1 since it wasn't given.

6y'' + y' + 19.6y = 0, solving for the initial conditions

.

.

.

y(x) = e^(-.08333x)(-0.1846sin(1.8055x)-4cos(1.0855x))

But that comes back as incorrect. I had a similar problem and didn't have any trouble so I'm having a hard time seeing where I went wrong with this one.

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# Homework Help: Modeling a Spring

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