A uniform rod is 2.0 m long. The rod is pivoted about a horizontal, frictionless pin through one end. The moment of inertia of the rod about this axis is given by (1/3)ML2. The rod is released from rest at an angle of 30° above the horizontal. What is the angular acceleration of the rod at the instant it is released?

Respuesta :

Answer:

Angular acceleration = 6.37rad/sec²

Approximately, Angular acceleration =

6.4 rad/sec²

Explanation:

Length of the rod = 2.0m long

Inclination of the rod (horizontal) = 30°

Mass of the rod is not given so we would refer to it as = M

Rotational Inertia of the Rod(I) = 1/3ML²

Angular Acceleration = ?

There is an equation that shows us the relationship between Torque and Angular acceleration.

The equation is :

Torque(T) = Inertia × Angular Acceleration

Angular acceleration = Torque ÷ Inertia

Where:

Torque = L/2(MgCosθ)

Where M = Mass

L = Length = 2.0m

θ = Inclination of the rod (horizontal) = 30°

g = Acceleration due to gravity = 9.81m/s²

Inertia = 1/3ML²

Angular Acceleration =  (Mass × g × Cos (30°) × (L÷2)) ÷ 1/3ML²

Angular Acceleration =

(3 × g × cos 30°) ÷ 2× L

Angular Acceleration = (3 × 9.81m/s² × cos 30°) ÷ 2× L

Angular Acceleration = 3 × 9.81m/s² × cos 30°) ÷ 2× 2.0m

Angular Acceleration = 6.37rad/sec²

Approximately Angular Acceleration =

6.4rad/sec²

Lanuel

The angular acceleration of the rod at the instant it is released is 6.37 [tex]rad/s^2[/tex].

Given the following data:

  • Length = 2 meter
  • Angle = 30°

To calculate the angular acceleration of the rod at the instant it is released:

The moment of inertia of the rod about a horizontal, frictionless pin through one end (axis) is given by the formula:

[tex](\frac{1}{3})ML^2[/tex]      ...equation 1.

Mathematically, torque is given by this formula:

[tex]T = I\alpha[/tex]    ....equation 2.

Where:

  • T represents torque.
  • I is the moment of inertia.
  • [tex]\alpha[/tex] is the angular acceleration.

Making [tex]\alpha[/tex] the subject of formula, we have:

[tex]\alpha =\frac{T}{I}[/tex]    ....equation 3.

For the horizontal component, torque is given by the formula:

[tex]Torque = \frac{L}{2}(MgCos\theta)[/tex]    ...equation 4

Substituting eqn 1 and eqn 4 into eqn 3, we have:

[tex]\alpha =\frac{\frac{L}{2}(MgCos\theta)}{(\frac{1}{3})ML^2} \\\\\alpha = \frac{\frac{MgCos\theta L}{2}}{\frac{ML^2}{3}} \\\\\alpha = \frac{MgCos\theta L}{2} \times \frac{3}{ML^2} \\\\\alpha = \frac{3gCos\theta}{2L} \\\\\alpha =\frac{\frac{L}{2}(MgCos\theta)}{(\frac{1}{3})ML^2} \\\\\alpha = \frac{\frac{MgCos\theta L}{2}}{\frac{ML^2}{3}} \\\\\alpha = \frac{MgCos\theta L}{2} \times \frac{3}{ML^2} \\\\\alpha = \frac{3gCos\theta}{2L} \\\\\alpha = \frac{3\;\times \;9.8 \times\; Cos30}{2\times 2}[/tex]

[tex]\alpha = \frac{29.4 \times\; 0.8660}{4}\\\\\alpha = \frac{25.46}{4}[/tex]

Angular acceleration, [tex]\alpha[/tex] = 6.37 [tex]rad/s^2[/tex]

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