Question: Problem 3 : Propeller coming to rest ( 1 0 points ) A motor is used to spin a submerged propeller that has two blades.
Problem : Propeller coming to rest points
A motor is used to spin a submerged propeller that has two blades. When the motor is running, the propeller spins with a constant angular velocity omegaimathrmradmathrms in the counterclockwise direction. At some moment of time, the motor shuts off. Suppose that the surrounding water exerts a constant drag force of magnitude N on each blade, perpendicular to each blade and opposite the direction of rotation, at a point m from the pivot. The moment of inertia of the propeller is Imathrm~kgcdot mathrm~m You can neglect gravity in this problem, See diagram below.
Hint: Pay careful attention to the signs of your answers in parts ab
a What is the net torque on the whole propeller?
b What is the angular acceleration of the propeller?
c What is the net work done by the surrounding water on the propeller as it comes to rest? Hint: The answer is negative and can be found without solving a and b using a certain theorem that we covered in class. A second way to solve this problem makes use of ab and a bit more.
d How much time does it take for the propeller to come to rest? If you did not solve part b you may assume that the angular acceleration is alphamathrmradmathrms for full credit on this part.
Bonus: When the motor is running, what power is the motor delivering to the propeller? Ptau omega
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