A uniform disk with mass m = 9.11 kg and radius R = 1.37 m lies in the x-y plane and centered at the origin. Three forces act in the +y-direction on the disk: 1) a force 319 N at the edge of the disk on the +x-axis, 2) a force 319 N at the edge of the disk on the –y-axis, and 3) a force 319 N acts at the edge of the disk at an angle θ = 32° above the –x-axis. 1) What is the magnitude of the torque on the disk about the z axis due to F1? N-m Submit 2) What is the magnitude of the torque on the disk about the z axis due to F2? N-m Submit 3) What is the magnitude of the torque on the disk about the z axis due to F3? N-m Submit 4) What is the x-component of the net torque about the z axis on the disk? N-m Submit 5) What is the y-component of the net torque about the z axis on the disk? N-m Submit 6) What is the z-component of the net torque about the z axis on the disk? N-m Submit 7) What is the magnitude of the angular acceleration about the z axis of the disk? rad/s2 Submit 8) If the disk starts from rest, what is the rotational energy of the disk after the forces have been applied for t = 1.5 s? J Submit

Respuesta :

Answer:

1) τ = 437 N m, 2)  τ = 437 N m , 3) τ = 344.4 N m ,  7) α  = 142.5 rad/s²  and

8)  Em = 1.95 105 J

Explanation:

The torque is given by the expression

    τ = F x R

Bold indicates vectors, we can calculate the magnitude of this torque with the expression

     τ = F R sin  θ

The direction is given by perpendicular to the two vectors F and R

1) To calculate the torque due to the F1 force. The angle between F1 and R is 90°

    sin 90 = 1

    τ = F R

    τ = 319 1.37

    τ = 437 N m

In the positive Z direction

2) The torque due to F2 again the angle is 90 ° without 90 = 1

    τ = F R

    τ = (-319) 1.37 sin 270

    τ = 437 N m

In the positive z direction

3) The torque  F3 where θ  = 32 ° measured from the negative side of the x axis

     τ = F R sin θ  

Angle is measured from the positive side of the x-axis, so this angle is

    θ  = 180 - 32 = 128 °

    τ = 319 1.37 sin 128

    τ = 344.4 N m

4) The x components of this torque is

    F1 R + F3 R cos 128 = 437 + 319 1.37 cos 128 = 437 + 269

    τₓ = 706 N m

5) the component and

     F2 R +F3 R sin 128 = 437 + 344.4

     τ y =  781.4 N m

The component has to be perpendicular to the moment

7) angular acceleration

    τ = I α

The moment of inertia of a disk is

    I = ½ M R²

    I = ½ 9.11 1.37²

    I = 8.55 Kg m²

    α  = τ / I

    α  = (τ1 + τ2 + τ3) / I

    α   = (437 + 437 + 344.4) / 8.55

    α  = 142.5 rad / s²

8) the disk starts at rest, let's calculate the speed in the given time

    w = w₀ + α  t

    w = 0 + 142.5  1.5

   w = 213.75 rad / s

Energy is

   Em = K = ½ I w²

   Em = ½ 8.55 213.75²

   Em = 1.95 105 J

Lanuel

The magnitude of the torque on the disk about the z-axis due to Force 1 (F1) is equal to 437.03 Newton.

Given the following data:

  • Mass of disk = 9.11 kg.
  • Radius of disk = 1.37 m.
  • Force 1 = 319 Newton.
  • Force 2 = 319 Newton.
  • Force 3 = 319 Newton.
  • Angle of inclination = 32°.
  • Time = 1.5 seconds.

How to determine the torque on the disk about the z.

Mathematically, the magnitude of the torque on the disk about the z-axis due to Force 1 (F1) is given by:

[tex]\tau_1 =F_1r_1 sin\theta_1\\\\\tau_1 = 319 \times 1.37 \times sin 90\\\\\tau_1 = 437.03\;Newton[/tex]

For the tension due to Force 2 (F2), we have:

[tex]\tau_2 =F_2r_2sin\theta_2\\\\\tau_2 = 319 \times 1.37 \times sin 180\\\\\tau_2 = 0\;Newton[/tex]

For the tension due to Force 3 (F3), we have:

[tex]\tau_3 =F_3r_3sin\theta_3\\\\\tau_3 = 319 \times 1.37 \times sin (90-32)\\\\\tau_3 = 370.62\;Newton[/tex]

Since the torque generated by Force 2 (F2) has a magnitude of zero and torque 2 and 3 are in the z-direction, there is no x-component of the net torque about the z-axis.

Similarly, there is no y-component of the net torque about the z-axis.

How to calculate the z-component of the net torque.

[tex]\tau_{n}=\tau_1 - \tau_3\\\\\tau_{n}=437.03-370.62\\\\\tau_{n}=66.41\;Newton[/tex]

How to calculate the magnitude of the angular acceleration.

First of all, we would determine the moment of inertia of the disk by using this formula:

[tex]I=\frac{1}{2} mr^2\\\\I=\frac{1}{2} \times 9.11 \times 1.37^2\\\\I=8.55\;kgm^2[/tex]

For the angular acceleration, we have:

[tex]\alpha =\frac{\tau_n}{I} \\\\\alpha =\frac{66.41}{8.55} \\\\\alpha =7.77\;rad/s^2[/tex]

How to calculate the rotational energy of the disk.

First of all, we would determine the angular velocity by using this formula:

[tex]\omega = \alpha t\\\\\omega =7.77 \times 1.5\\\\\omega =11.66\;rad/s[/tex]

For the rotational energy, we have:

[tex]K.E=\frac{1}{2} I\omega^2\\\\K.E=\frac{1}{2} \times 8.55 \times 11.66^2\\\\K.E =581.21\;Joules[/tex]

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