The disk on the bottom has a rotational inertia of I0 and is spinning clockwise on a horizontal surface having negligible friction at an angular speed of 3ω0. The top disk is then dropped directly on top of the bottom disk. The top disk has a rotational inertia of I0 and was initially spinning counterclockwise at an angular speed of ω0. If the initial total kinetic energy of the two-disk system was E0, what will the kinetic energy of the system be once the objects reach a common angular speed?

Respuesta :

Answer:

  K = I₀ w₀²

Explanation:

This is a problem of conservation of angular momentum,

We take the counterclockwise turn as positive

Initial. Before the crash

       L₀ = -I₀ 3w₀ + I₀ w₀

Final. The two albums together

       [tex]L_{f}[/tex]= (I₀ + I₀) wf

The moment is preserved

      L₀ =  [tex]L_{f}[/tex]

      -I₀ 2w₀ = (2I₀)  [tex]w_{f}[/tex]

        [tex]w_{f}[/tex] = -w₀

Let's look for kinetic energy

       K = ½ I w²

initial

       K₀ = ½ I₀ (-3w₀)² + ½ I₀ w₀²

       K₀ = ½ I₀ w₀² (9-1)

       K₀ = 4 I₀ w₀² = E₀

Final

        K = ½ 2 I₀ (-w₀)²

         K = I₀ w₀²

The kinetic energy of the system is [tex]I_0 \omega _0^2[/tex] object reaches a common angular speed.

What is Kinetic energy?

It is defined as the energy of an object or body due to the motion of the object.

From the conservation of angular momentum,  

Assume the counterclockwise turn is positive,  

Before the crash,  

[tex]L_0 = - I_o \times 3\omega _0 + I_0\omega _0[/tex]  

Final. The two disk together  

= [tex](I_0 +I_0 ) \omega _f[/tex]  

Since the moment is preserved  

[tex]L_0 = L_f[/tex]  

[tex]I_0 \times 2 \omega _0 = 2I_0 \times \omega _f[/tex]    

[tex]\omega _f = \omega _0[/tex]  

For kinetic energy  

[tex]K = \dfrac 12 I\omega ^2[/tex]  

initial Kinetic energy,  

[tex]K_0= \dfrac 12 I_0 ( -3\omega _0)^2 + \dfrac 12 I_0 w_0^2\\\\\K_0 = \dfrac 12 I_0 w_0^2 (9-1)\\\\K_0 = 4 I_0 \omega ^2[/tex]  

Final kinetic energy,  

[tex]K = \dfrac 12 2I_0 (-\omega _0)^2\\\\K = I_0 \omega _0^2[/tex]    

Therefore, the kinetic energy of the system is [tex]I_0 \omega _0^2[/tex]object reaches a common angular speed.

To know more about the disk's kinetic energy,

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