What is the Force and Tension in a Helicopter Truck Rescue?

[jungleismassiv]

After an incident over the mid-semester break involving a packet of Maltesers, a flooded creek,
and a wombat, a 15,000 kg salvage helicopter is lifting a 4,500 kg truck with an upward
acceleration of 1.4 m.s-2. Calculate:
1) The force the air exerts on the helicopter blades.
2) The tension in the cable between the truck and the helicopter

1. F = ma, so we know the mass is (15000 + 4500)

and would the acceleration be (9.8 + 1.4)?

2. Would T = m1*g + m1a?

 

[Corneo]

The accelerations are in opposite directions. If you define the direction up as positive then g = -9.8 m/s^2.

 

[jungleismassiv]

The accelerations are in opposite directions. If you define the direction up as positive then g = -9.8 m/s^2.

Yes, but will the 1.4 be negative as well because the overall acceleration should be greater than 9.8?

 

[ramollari]

No, the acceleration is what it is: 1.4m/s^2. You can take the upward direction as positive, so any downward pointing force is negative, and any upward pointing force is positive.