Finding Joules of heat for 75% efficient motor at 250hp.

AI Thread Summary
To find the Joules of heat produced by a 75% efficient motor requiring 0.250 hp, the conversion from horsepower to watts is necessary, resulting in 139 watts when applying the efficiency. The correct calculation involves recognizing that 25% of the input energy is converted to heat, leading to the conclusion that the motor produces 168 kJ of heat per hour. The confusion arises from incorrectly applying the efficiency percentage in the initial calculations. Ultimately, the correct approach confirms that the motor generates significant heat due to its inefficiency. Understanding the relationship between efficiency and heat production is crucial for accurate calculations.
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Homework Statement


Forgive me for any indiscretions my first post.

The problem is to find the Joules of heat per hour produced in a motor that is 75% efficient and requires 0.250hp to run it.

Homework Equations



efficiency=1-(Qc/Qh)

The Attempt at a Solution



1. convert hp to Watts; 0.250hp* 746W/hp *75 percent=139W

At this point the answer is wrong and I don't know why. I have tried for hours to solve this please help!
 
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Try multiplying by 25 percent instead. 75% efficient means that 25% of the applied work is converted to heat.
 
I did the problem is that gives me a small number at around 48 the bok says the answer is 168KJ


It's 139 when I multiply by 75%
 
I don't know then. Would you mind typing out the problem exactly as it is stated?
 
No problem.

How many joules of heat per hour are produced in a motor that is 75.0 percent efficient and requires 0.250hp to run it? Ans 168kJ
 

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