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8090 [49]
2 years ago
7

A motor keep a Ferris wheel (with moment of inertia 6.97 × 107 kg · m2 ) rotating at 8.5 rev/hr. When the motor is turned off, t

he wheel slows down (because of friction) to 7.5 rev/hr in 15 s. What was the power of the motor that kept the wheel rotating at 8.5 rev/hr despite friction?
Physics
1 answer:
Talja [164]2 years ago
8 0

Answer:

P = 133.13 Watt

Explanation:

Initial angular speed of the ferris wheel is given as

\omega_i = 2\pi f

\omega_i = 2\pi(8.5/3600)

\omega_i = 0.015 rad/s

final angular speed after friction is given as

\omega_f = 2\pi f

\omega_f = 2\pi(7.5/3600)

\omega_f = 0.013 rad/s

now angular acceleration is given as

\alpha = \frac{\omega_f - \omega_i}{\Delta t}

\alpha = \frac{0.015 - 0.013}{15}

\alpha = 1.27 \times 10^{-4} rad/s^2

now torque due to friction on the wheel is given as

\tau = I \alpha

\tau = (6.97 \times 10^7)(1.27 \times 10^{-4})

\tau = 8875.3 N m

Now the power required to rotate it with initial given speed is

P = \tau \omega

P = 8875.3 \times 0.015

P = 133.13 Watt

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Answer:

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Explanation:

v₀ = initial speed of the hand = 4.75 m/s

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F = - 2677.3 N

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