Calculating Forces in a Helicopter Lift: F=ma and Cable Tension

[runningirl]

Homework Statement

A 7000 kg helicopter accelerates upward at 0.70 m/s/s while lifting a 1000 kg car to a mountaintop for a TV commercial photo shoot.

a) What is the downward force exerted on the air by the rotors of the helicopter?

b) A steel cable is used to connect the car to the helicopter. What tension must the cable be able to withstand without breaking? (treat the mass of the cable as negligible)

Homework Equations

F=ma

The Attempt at a Solution

for part a, I used the f=ma equation and got the downward force to be 4900 N. But I'm not sure if I did it correctly.
I'm not sure about part b, do I use the force from part a and use the f=ma equation...?

 

[AeroSpaceX]

hmm let me try out this qn.

for part (a), if I am not wrong, the downward force exerted on the air by the rotors of the helicopter is much greater than your ans.

*assume that the combined mass of the helicopter and car to be 8000kg, and no air resistance
the lift required to accelerate the combined mass up at 0.7ms^-2 is equal and opposite to the force exerted on the air by the rotors by Newton's 3rd Law

For part (b), one way to approach the problem is to isolate either the car or the helicopter and draw a free body diagram. For instance, considering the car by itself, (upwards as the reference direction), F_y=T-W_car=m_cara

If you are considering the helicopter instead, you need part (a) to solve for T

 

[runningirl]

we haven't learned about Newton's third law yet.
is there any way to figure out part a with just using Newton's second law or any equations of motion?