Helicopter Lifting off(Newtons Laws). Help please?

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SUMMARY

The discussion revolves around calculating the upward force required for a medical helicopter weighing 7000 lbs to lift off with an acceleration of 10 ft/s². The relevant equations include T - w = ma and w = mg, where T is the thrust, w is the weight, m is mass, and a is acceleration. The correct approach involves recognizing that the total upward acceleration must counteract both gravitational acceleration and the additional upward acceleration, leading to the conclusion that the thrust must equal the weight plus the force needed for the upward acceleration.

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Homework Statement


A medical helicopter weighs 7000 lbs. How much upward force must the propeller supply for it to lift off at 10ft/sec(squared)?


Homework Equations



T-w=ma, w=mg

The Attempt at a Solution


Here is what I tried:
T-w=ma.....w=mg---7000=m(32.2)=217.39k
T-7000= 217.39(-10ft/s)
T=4826.1

What am I doing wrong here? Shouldnt the acceleration be a negative value since it is going upward? and what should the actual final answer be?
 
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F = m * a

now, to go up, it must counter both gravitational acceleration, plus add that additional 10 ft/sec acceleration

so "a" = 10 ft/sec + ...
 
I see, thank you.
So technically, the only thing I did wrong was the negative sign.
 
Yeah, because if you're doing T-w then you're saying that 'g' is acting in the negative direction since you're subtracting it from upward force. Since the 10 ft/s are in the opposite direction from g, it can't be negative TOO
 

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