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chemguy990
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Homework Statement
A 5400 kg helicopter accelerates upward at 2.17 m/s2. The acceleration due to gravity is 9.8 m/s2. What life force is exerted by the air on the propellers? Answer in N.
Homework Equations
Fnet=ma
The Attempt at a Solution
I am making the acceleration positive (2.17m/s2) and the gravitational acceleration negative (-9.8 m/s2) since the helicopter is traveling upwards.
F(lift) - F(gravity) = ma
F(lift) - (5400kgx(-9.8m/s2)) = (5400kg)(2.17 m/s2)
F(lift) = 11718-52920 N
F(lift) = -41202 N
Shouldnt the lift force acting upon the propellers by positive?