SOLUTION: Bobby McG (who has a mass of 70kg) jumps out of an airplane and notices that she starts to accelerate at a rate of 6m/s^2. What is the force of gravity acting on Bobby?

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Question 1071394: Bobby McG (who has a mass of 70kg) jumps out of an airplane and notices that she starts to accelerate at a rate of 6m/s^2.
What is the force of gravity acting on Bobby?
Found 2 solutions by ikleyn, KMST:
Answer by ikleyn(52890) About Me  (Show Source):
You can put this solution on YOUR website!
.
F = ma, Newton's second law.



Answer by KMST(5328) About Me  (Show Source):
You can put this solution on YOUR website!
I do not think anyone, on Earth, jumps of an airplane and starts to accelerate at a rate of 6m/s^2. The initial downwards acceleration rate should be 9.7 - 9.8 m/s^2, no matter how high your airplane is flying, and it should take several seconds of increasing downwards speed and increasing air drag force to reach an acceleration of 6m/s^2.
At that point the acceleration has little to do with the force of gravity.
The net force acting upon a 70kg body accelerating at 6m/s^2 is 4200 Newtons:
%2870kg%29%2860m%2Fs%5E2%29=4200N .
However, that is not the "force of gravity." It is the sum of the downwards force of gravity, and a substantial upwards air resistance force.