12*8A hollow steel ball weighing 4 pounds is suspended from a spring. This stretches the spring 13 feet. The ball is started in motion from the equilibrium position with a downward velocity of 2 feet per second. The air resistance (in pounds) of the moving ball numerically equals 4 times its velocity (in feet per second) . Suppose that after t seconds the ball is y feet below its rest position. Find y in terms of t. (Note that the positive direction is down.) Take as the gravitational acceleration 32 feet per second per second

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Answer:

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Explanation:

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[tex]y[/tex] term against the [tex]t[/tex] can be calculated by the damped vibration equation.[tex]y[/tex] term against the [tex]t[/tex] is,

[tex]y(t) = \dfrac 9{16} e^{-8t} - \dfrac 9{16} e^{-24t}[/tex]

What is Newton's second law?

The force applied to an object is directly proportional to the mass and acceleration of the object.

[tex]F = mg[/tex]

F  = force= 4 pounds

m - mass = ?

g - gravitaional acceleration =[tex]\bold {32\ ft/s^2}[/tex]

So,

[tex]m= \dfrac 4{32}\\\\m = \dfrac 18[/tex]

Form Hook's law,

[tex]F= kx[/tex]

Where,

[tex]x[/tex]- the distance of stretch = 1/6 ft,

Do,

[tex]4 = k (\dfrac 16)\\k = 24\rm \ lb/ft[/tex]

As given in the question,

The air resistance is 4 times greater than the velocity,

So, the damped vibration of the spring-mass system,

[tex]m \dfrac {d^2y}{dt^2}+ c \dfrac {dy}{dt} + ky = 0[/tex]

Put the values in the formula,

[tex](\dfrac 18) \dfrac {d^2y}{dt^2}+ (4) \dfrac {dy}{dt} + (24)y = 0\\\\\dfrac {d^2y}{dt^2}+ (32) \dfrac {dy}{dt} + (192)y = 0[/tex]

Thus, [tex]y[/tex] term against the [tex]t[/tex] is,

[tex]y(t) = \dfrac 9{16} e^{-8t} - \dfrac 9{16} e^{-24t}[/tex]

To know more about  damped vibration,

https://brainly.com/question/7229759