What is the lift force exerted by the air on the rotors?

[thschica]

A 6520 kg helicopter accelerates upward at 0.57 m/s2 while lifting a 1190 kg car.
(a) What is the lift force exerted by the air on the rotors?
_________ N
(b) What is the tension in the cable (ignore its mass) that connects the car to the helicopter?
_____N

I have no idea how to do this and it is going to be on my mid-term.
Can someone please help me because I keep getting very strange numbers.
I used a kinetics equation but the answer was wrong!

 

[daniel_i_l]

Use Newtons second law: F=ma.
For (a) find out how much force is needed to accelerate both of the masses. The tension only accelerates the car.

 

[lando45]

If you apply Newton's Second Law to part (a) you can find the answer relatively easily; for the M value, just make sure you use the composite mass. You know a, as it's given in the question, so F can easily be solved. I think for part (b) you can just use Newton's Second Law, but remember the only mass involved is that of the suspended car. The acceleration should remain the same though...

 

[thschica]

should a) be 4394.7
and b) be 3716.4