uniform disk with mass 40.0 kg and radius 0.200 m is pivoted at its center about a horizontal, frictionless axle that is stationary. The disk is initially at rest, and then a constant force 퐹=30.0푁is applied tangent to the rim of the disk.a) What is the magnitude 푣of the tangential velocity of a point on the rim of the disk after the disk has turned through 0.200 revolution?b) What is the magnitude 푎of the resultant acceleration of that point in part a?

Respuesta :

Answer:

The magnitude of the tangential velocity is [tex]v= 0.868 m/s[/tex]

The magnitude of the resultant acceleration at that point is  [tex]a = 4.057 m/s^2[/tex]

Explanation:

From the question we are told that

      The mass of the uniform disk is [tex]m_d = 40.0kg[/tex]

       The radius of the uniform disk is [tex]R_d = 0.200m[/tex]

       The force applied on the disk is [tex]F_d = 30.0N[/tex]

Generally the angular speed i mathematically represented as

             [tex]w = \sqrt{2 \alpha \theta}[/tex]

Where [tex]\theta[/tex] is the angular displacement given from the question as

           [tex]\theta = 0.2000 rev = 0.2000 rev * \frac{2 \pi \ rad }{1 rev}[/tex]

                 [tex]=1.257\ rad[/tex]

   [tex]\alpha[/tex] is the angular acceleration which is mathematically represented as

                    [tex]\alpha = \frac{torque }{moment \ of \ inertia} = \frac{F_d * R_d}{I}[/tex]

    The moment of inertial is mathematically represented as

                     [tex]I = \frac{1}{2} m_dR^2_d[/tex]

Substituting values

                    [tex]I = 0.5 * 40 * 0.200^2[/tex]

                        [tex]= 0.8kg \cdot m^2[/tex]

Considering the equation for angular acceleration

               [tex]\alpha = \frac{torque }{moment \ of \ inertia} = \frac{F_d * R_d}{I}[/tex]

Substituting values

               [tex]\alph[/tex][tex]\alpha = \frac{(30.0)(0.200)}{0.8}[/tex]

                   [tex]= 7.5 rad/s^2[/tex]

Considering the equation for angular velocity

    [tex]w = \sqrt{2 \alpha \theta}[/tex]

Substituting values

     [tex]w =\sqrt{2 * (7.5) * 1.257}[/tex]

         [tex]= 4.34 \ rad/s[/tex]

The tangential velocity of a given point on the rim is mathematically represented as

                 [tex]v = R_d w[/tex]

Substituting values

                    [tex]= (0.200)(4.34)[/tex]

                     [tex]v= 0.868 m/s[/tex]

The radial acceleration at hat point  is mathematically represented as

            [tex]\alpha_r = \frac{v^2}{R}[/tex]

                  [tex]= \frac{0.868^2}{0.200^2}[/tex]

                 [tex]= 3.7699 \ m/s^2[/tex]

The tangential acceleration at that point is mathematically represented as

               [tex]\alpha _t = R \alpha[/tex]

Substituting values

           [tex]\alpha _t = (0.200) (7.5)[/tex]

                 [tex]= 1.5 m/s^2[/tex]

The magnitude of resultant acceleration at that point is

                 [tex]a = \sqrt{\alpha_r ^2+ \alpha_t^2 }[/tex]

Substituting values

                [tex]a = \sqrt{(3.7699)^2 + (1.5)^2}[/tex]

                   [tex]a = 4.057 m/s^2[/tex]

         

(a) The tangential velocity of a point on the rim of the disk is

v = √10g(H−R)/7

(b) The magnitude of the resultant acceleration is given by

a = 10g(H−R)/(7R)

Rotational motion:

(a) From the law of conservation of energy:

PE(initial) + KE(initial) = PE(final) + KE(final) + RE

initialy Kinetic energy is 0

RE represents the rotational kinetic energy

mgH = mgR + ½mv² + ½Iω²

here I is the moment of inertia of the sphere

mgH = mgR + ½mv² + ½(⅖mr²)(v/r)²

mgH = mgR + ½mv² + ⅕mv²

gH = gR + ⁷/₁₀ v²

v² = 10g(H−R)/7

v = [tex]\sqrt{10g(H-R)/7}[/tex] will be the tangential velocity of a point on the rim of the disk.

(b)The normal force exerted by the track on the sphere will be:

N = mv²/R

N = m (10g(H−R)/7) / R

N = 10mg(H−R)/(7R) = ma

So, acceleration is given by:

a = 10g(H−R)/(7R)

Learn more about conservation of energy:

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