Problem: Consider a motor that exerts a constant torque of 25.0 to a horizontal platform whose moment of inertia is 50.0 . Assume that the platform is initially at rest and the torque is applied for 12.0 . Neglect friction.Part A ) How much work  does the motor do on the platform during this process?Enter your answer in joules to four significant figures. = Part B ) What is the rotational kinetic energy of the platform  at the end of the process described above?Enter your answer in joules to four significant figures. = Part C ) What is the angular velocity  of the platform at the end of this process?Enter your answer in radians per second to three significant figures. = Part D ) How long  does it take for the motor to do the work done on the platform calculated in Part A?Enter your answer in seconds to three significant figures. = Part E ) What is the average power  delivered by the motor in the situation above?Enter your answer in watts to three significant figures. = Part F ) Note that the instantaneous power  delivered by the motor is directly proportional to , so  increases as the platform spins faster and faster. How does the instantaneous power  being delivered by the motor at the time  compare to the average power  calculated in Part E?Note that the instantaneous power delivered by the motor is directly proportional to , so increases as the platform spins faster and faster. How does the instantaneous power being delivered by the motor at the time compare to the average power calculated in Part E?a.b.c.d.none of the above

FREE Expert Solution

This problem involves rotational kinematics. The approach is simple and straightforward.

Angular acceleration is expressed as:

α=τI, where τ is torque and I is the moment of inertia. 

Part A)

Work done:

W=τθ

We're given τ = 25.0 N•m

I = 50.0 kg•m2

Therefore, the angular acceleration is:

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Problem Details

Consider a motor that exerts a constant torque of 25.0N \cdot m to a horizontal platform whose moment of inertia is 50.0kg \cdot m^2 . Assume that the platform is initially at rest and the torque is applied for 12.0rotations . Neglect friction.


Part A ) How much work W does the motor do on the platform during this process?

Enter your answer in joules to four significant figures.

W =\rm J


Part B ) What is the rotational kinetic energy of the platform K_rot,f at the end of the process described above?

Enter your answer in joules to four significant figures.

K_rot,f =\rm J

Part C ) What is the angular velocity omega_f of the platform at the end of this process?

Enter your answer in radians per second to three significant figures.

omega_f ={\rm rad / s}

Part D ) How long \Delta t does it take for the motor to do the work done on the platform calculated in Part A?

Enter your answer in seconds to three significant figures.

\Delta t =


 \rm s

Part E ) What is the average power P_avg delivered by the motor in the situation above?

Enter your answer in watts to three significant figures.

P_avg = \rm W

Part F ) Note that the instantaneous power P delivered by the motor is directly proportional to omega, so P increases as the platform spins faster and faster. How does the instantaneous power P_f being delivered by the motor at the time t_{\rm f} compare to the average power P_avg calculated in Part E?

Note that the instantaneous power delivered by the motor is directly proportional to , so increases as the platform spins faster and faster. How does the instantaneous power being delivered by the motor at the time compare to the average power calculated in Part E?

a.P = P_{\rm avg}
b.P = 2 * P_{\rm avg}
c.P = P_{\rm avg} / 2
d.none of the above

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