A) What is the magnitude of the tangential acceleration of a bug on the rim of a 12.5-in.-diameter disk if the disk accelerates uniformly from rest to an angular speed of 75.0 rev/min in 3.20 s?
B) When the disk is at its final speed, what is the tangential velocity of the bug?C) One second after the bug starts from rest, what is its tangential acceleration?D) One second after the bug starts from rest, what is its centripetal acceleration?E) One second after the bug starts from rest, what is its total acceleration?

Respuesta :

Answer:

0.38963 m/s²

1.246819325 m/s

0.38963 m/s²

0.95629 m/s²

1.03261 m/s² and 22.17°

Explanation:

d = Diameter of rim = 12.5 in = [tex]12.5\times 0.0254=0.3175\ m[/tex]

r = Radius = [tex]\frac{d}{2}=\frac{0.3175}{2}=0.15875\ m[/tex]

[tex]\omega_f[/tex] = Final angular velocity = [tex]75\times\frac{2\pi}{60}=7.85398\ rad/s[/tex]

[tex]\omega_i[/tex] = Initial angular velocity = 0

[tex]\alpha[/tex] = Angular acceleration

t = Time taken = 3.2 s

Equation of rotational motion

[tex]\omega_f=\omega_i+\alpha t\\\Rightarrow \alpha=\frac{\omega_f-\omega_i}{t}\\\Rightarrow \alpha=\frac{7.85398-0}{3.2}\\\Rightarrow \alpha=2.45436875\ rad/s^2[/tex]

Tangential acceleration is given by

[tex]a_t=r\alpha\\\Rightarrow a_t=0.15875\times 2.45436875\\\Rightarrow a_t=0.38963\ m/s^2[/tex]

The tangential acceleration of the bug is 0.38963 m/s²

Tangential velocity is given by

[tex]v=r\omega\\\Rightarrow v=0.15875\times 7.85398\\\Rightarrow v=1.246819325\ m/s[/tex]

The tangential velocity of the bug is 1.246819325 m/s

The tangential acceleration is constant which is 0.38963 m/s²

Centripetal acceleration is given by

[tex]a_c=\frac{a_tt^2}{r}\\\Rightarrow a_c=\frac{0.38963^2\times 1}{0.15875}\\\Rightarrow a_c=0.95629\ m/s^2[/tex]

The centripetal acceleration of the bug is 0.95629 m/s²

The resultant of the acceleration gives us total acceleration

[tex]a=\sqrt{a_t^2+a_c^2}\\\Rightarrow a=\sqrt{0.38963^2+0.95629^2}\\\Rightarrow a=1.03261\ m/s^2[/tex]

Direction is given by

[tex]\theta=cos^{-1}\frac{a_c}{a}\\\Rightarrow \theta=cos^{-1}\frac{0.95629}{1.03261}\\\Rightarrow \theta=22.17^{\circ}[/tex]

The magnitude and direction of the acceleration is 1.03261 m/s² and 22.17°

Lanuel

a. The magnitude of the tangential acceleration of a bug on the rim is[tex]alpha = 2.45\;rad/s^2[/tex]

b. The tangential velocity of the bug, when the disk is at its final speed is  1.25 m/s.

c. The tangential acceleration, one second after the bug starts from rest is [tex]alpha_t = 0.39\; m/s^2[/tex]

d. The centripetal acceleration, one second after the bug starts from rest is [tex]alpha_c = 0.96 \;m/s^2[/tex]

e. The total acceleration, one second after the bug starts from rest is [tex]T_a = 1.04 \; m/s^2[/tex]

Given the following data:

  • Diameter = 12.5 inches
  • Initial angular velocity = 0 rev/min (since the disk is at rest).
  • Final angular velocity = 75.0 rev/min
  • Time = 3.20 seconds.

Conversion:

1 rev/min = 0.1047 rad/s

75.0 rev/min = X rad/s

Cross-multiplying, we have:

[tex]X = 75 \times 0.1047[/tex]

X = 7.85 rad/s

[tex]Radius = \frac{Diameter}{2} = \frac{12.5}{2} = 6.25\; in[/tex]

1 inch = 0.0254 meter

6.25 inches = 0.1588 meter

a. To find the magnitude of the tangential acceleration of a bug on the rim:

[tex]\alpha = \frac{w_f \; -\;w_i}{t} \\\\\alpha = \frac{ 7.85\; -\;0}{3.2}\\\\\alpha = 2.45\;rad/s^2[/tex]

b. To find the tangential velocity of the bug, when the disk is at its final speed:

[tex]V = rw\\\\V = 0.1588 \times 7.85[/tex]

V = 1.25 m/s

c. To find the tangential acceleration, one second after the bug starts from rest:

[tex]\alpha_t = r \alpha\\\\\alpha_t = 0.1588 \times 2.45\\\\ \alpha_t = 0.39\; m/s^2[/tex]

d. To find the centripetal acceleration, one second after the bug starts from rest:

[tex]\alpha_c = \frac{\alpha_t^2 t^2}{r} \\\\\alpha_c = \frac{ (0.39 \times1)^2}{0.1588}\\\\\alpha_c = \frac{ 0.1521}{0.1588}\\\\\alpha_c = 0.96 \;m/s^2[/tex]

e. To find the total acceleration, one second after the bug starts from rest:

Note: The total acceleration is the same as the resultant acceleration possessed by an object along a circular path.

[tex]T_a = \sqrt{\alpha_t^2 + \alpha_c^2 } \\\\T_a = \sqrt{0.39^2 + 0.96^2 }\\\\T_a = \sqrt{0.1521 + 0.9216 }\\\\T_a = \sqrt{1.0737 }\\\\T_a = 1.04 \; m/s^2[/tex]

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