Acceleration of the helicopter as it starts to rise

AI Thread Summary
The problem involves calculating the acceleration of a helicopter with a mass of 2500 kg, which propels 2400 kg of air downward at a speed of 11 m/s. The net force is calculated as 26400 N, factoring in the weight of the helicopter. The correct acceleration is derived from the equation 26400 - 2500(9.81) = (2500)a, leading to an acceleration of 0.75 m/s². However, there is confusion as the expected answer is 9.58 m/s², suggesting a possible error in the mass used in the calculations. Clarification on the textbook source indicates a potential misprint in the problem statement.
anlenemilk
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Homework Statement


At take off, the rotor blades of a helicopter propel 2400 kg of air vertically downwards each second. The air, intially at rest, is given a speed of 11ms^-1
QN: the mass of the helicopter is 2500 kg. Find the acceleration of the helicopter as it starts to rise



Homework Equations



<F>=Change in momentum /change in time
Fnet=ma

The Attempt at a Solution



<F>=Change in momentum /change in time
= (2400*11-0)/1= 26400N
26400-2500(9.81)=(2500)a
a=0.75ms^-2

The answer is 9.58ms^-2
I have no idea how to get this answer! HELP ME! THANK YOU VERY MUCH
 
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I'd say that your answer is correct and the given answer is wrong.

What textbook is this problem from?
 
anlenemilk said:
26400-2500(9.81)=(2500)a
Note that you'll get the given answer if you changed one of the masses to 250 (which is clearly wrong):
26400-250(9.81)=(2500)a​
That could be how the wrong answer was attained.
 
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