A mass of 4kg stretches a spring 40cm. Suppose the mass is displaced an additional 12cm in the positive (downward) direction and then released. Suppose that the damping constant is 3 N⋅s/m and assume g=9.8m/s2 is the gravitational acceleration. (a) Set up a differential equation that describes this system. Let x t

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Answer:

A differential equation is [tex]4x''+3x'+98x=0[/tex].

Explanation:

Given that,

Mass = 4 kg

Stretch string = 40 cm

Additional distance = 12 cm

Damping constant = 3 N-s/m

Let xx to denote the displacement, in meters, of the mass from its equilibrium position, and give your answer in terms of x,x′,x′′ .

We need to calculate the spring constant k

The net force in y direction at equilibrium position

[tex]F_{y}=0[/tex]

[tex]mg-kx=0[/tex]

Put the value into the formula

[tex]4\times9.8-k\times40\times10^{-2}=0[/tex]

[tex]k=\dfrac{4\times9.8}{40\times10^{-2}}[/tex]

[tex]k=98\ N/m[/tex]

The initial displacement from equilibrium

[tex]x(0)=12\ cm[/tex]

The initial velocity is

[tex]v(0)=0[/tex]

We need to set up a differential equation

The net force in y direction is zero at equilibrium position .

[tex]\Sum F_{y}=0[/tex]

[tex]mx''+cx'+kx=0[/tex]

Put the value into the equation

[tex]4x''+3x'+98x=0[/tex]

Hence, A differential equation is [tex]4x''+3x'+98x=0[/tex].

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