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A mass of 13kg stretches a spring 14cm. The mass is acted on by an external force of 6sin(t/2)N and moves in a medium that imparts a viscous force of 4N when the speed of the mass is 12cm/s. If the mass is set in motion from its equilibrium position with an initial velocity of 4cm/s4cm/s, determine the position uu of the mass at any time tt. Use 9.8m/s29.8m/s2 as the acceleration due to gravity. Pay close attention to the units.

Respuesta :

Answer:

[tex]13u\prime\prime+33.33u\prime+910u=6sin\frac{t}{2}, \ u(0)=0,u\prime(0)=0.04\\[/tex]

#Where [tex]u[/tex] is in meters and [tex]t[/tex] in seconds.

Explanation:

Given that :[tex]m=13.0kg, \ L=0.14m, \ F(t)=6sin\frac{t}{2}N, F_d(t*)=-4N^{-1}, u\prime(t*)=0.12m/s\\u(0)=0,u\prime(0)=0.04m/s[/tex]

From [tex]\omega=kL[/tex] we have:

[tex]k=\frac{\omega}{L}=\frac{mg}{0.14m}=\frac{13.0\times 9.8m/s}{0.14m}\\\\k=910kg/s^2[/tex]

From [tex]F_d(t)=-\gamma u\prime(t)[/tex] we have that:

[tex]\gamma=-\frac{F_d(t*)}{u\prime(t*)}=\frac{4N}{0.12m/s}\\=33.33Ns/m[/tex]

Now,given that the initial value problem is given by:

[tex]13u\prime\prime+33.33u\prime+910u=6sin\frac{t}{2}, \ u(0)=0,u\prime(0)=0.04\\[/tex]

Hence,the position of u at time t is given by

[tex]13u\prime\prime+33.33u\prime+910u=6sin\frac{t}{2}, \ u(0)=0,u\prime(0)=0.04\\[/tex], [tex]u[/tex] in meters,[tex]t[/tex] in seconds.