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# Power Question watch

1. This is the question I have:

An airplane flies horizontally at 55.0 m/s. Its propeller delivers 1500N of thrust (forward force) to overcome aerodynamic drag (backward force). Using dimensional reasoning and unity conversion ratios, calculator the useful power delivered by the propeller in units of kW and horsepower.

It kind of seems easy, but I dont quite get it or know what to do.
2. Dimensional reasoning means that you should look at the units on both sides of the equation and work out what the formula should be. Start by saying
Power = k Fⁿ x vª
and working out what n and a need to be to balance the units (dimensions) on either side of the formula.
k is a dimensionless constant which you can put equal to 1 (unity conversion ratio)
F is kg m /s/s
v is m/s
Power is .....
etc

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Updated: September 25, 2010
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