What is the efficiency of the aircraft engines in this scenario?

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Homework Help Overview

The discussion revolves around calculating the efficiency of aircraft engines based on given parameters, including mass, altitude, speed, and power output. The subject area pertains to physics, specifically energy, power, and efficiency calculations in the context of aviation.

Discussion Character

  • Exploratory, Assumption checking, Mathematical reasoning

Approaches and Questions Raised

  • Participants discuss the method for calculating efficiency, questioning unit conversions and the accuracy of their calculations. There is a focus on ensuring proper conversion of time, distance, and power units.

Discussion Status

Some participants have provided guidance on necessary unit conversions, while others express uncertainty about their calculations. Multiple interpretations of the problem are being explored, with no explicit consensus reached on the correct approach.

Contextual Notes

Participants are addressing potential errors in unit conversions, which are critical for accurate calculations in this problem. There is an emphasis on the importance of converting all measurements to consistent units before performing calculations.

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A 3.25 * 103-kg aircraft takes 12.5 min to achieve its cruising altitude of 10.0 km and cruising speed of 850 km/h. If the plane's engines deliver, on the average, 1500 hp of power during this time, what is the efficiency of the aircraft engines?

I initially believed the power out would be: (Kinetic energy + Potential energy)/Time

And efficiency would be 1500hp/power out. But after my calculations, I got 14.6% efficiency, when it should be 48.7% efficiency.

What did I do wrong?
 
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I calculated 48.8% efficiency.

Did you...

1) Change minutes to seconds?
2) Change km to m?
3) Change km/h to m/s?
4) Convert J to hp? ( 735.498 75 watt = 1hp/s)

You have to do each of those in this problem.
 
Check your units. Did you convert the power in hp to watts?

1 hp = 746 watts.
 
Looks like we typed at the same time.
 
I don't know what I did wrong.
I'm pretty sure I converted everything.
It must have been a calculation error, because I just got the right answer.
 

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