Rotational Motion: Calculating Time to Reach 750 RPM

AI Thread Summary
To calculate the time it takes for a 1.5 hp motor to accelerate a 4.5 kg disk to 750 RPM, one must understand the relationship between power, torque, and angular acceleration. The horsepower can be converted to watts to determine the torque produced by the motor. The angular acceleration can then be calculated using the torque and the moment of inertia of the disk. Once the angular acceleration is known, the time to reach the desired RPM can be determined using kinematic equations for rotational motion. Understanding these relationships is key to solving the problem effectively.
hannah12345
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Homework Statement


A 1.5 hp motor drives a machine disk having a mass of 4.5 kg and a diameter of .4 m from rest to a speed of 750 rpm. How long does it take to reach the operating speed?

Homework Equations


angular momentum
torque

The Attempt at a Solution


I'm not really sure where to start with this problem. I don't know how to find time without distance or acceleration. I tried solving for acceleration but I'm not sure how horsepower relates to torque.
 
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How much energy will the disk have at operating speed?
 
How would I use that to find time?
 
hannah12345 said:
How would I use that to find time?
What is the relationship between power, energy and time?
 

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