Helicopter accelerates while liftin what are the forces' magnitudes?

[Natali]

Homework Statement

A 7690 kg helicopter accelerates upward at 0.80 m/s2 while lifting a 1260 kg frame at a construction site. (a) What is the lift force exerted by the air on the helicopter rotors? (b) What is the tension in the cable (ignore its mass) that connects the frame to the helicopter? (c) What force does the cable exert on the helicopter?

Homework Equations

Newtons laws of motion

The Attempt at a Solution

draw free body diagram for both objects. use second law of motion.
what does it mean by "helicopter rotors"? the cable gives tension but it refers to the "force the cable exerts" as something seperate...

 

[physics girl phd]

helicopter rotors (blades) are just providing a lift force (through aerodynamics processes).

The tension in the cable IS the force the cable exerts on the copter.

Don't get bogged down by wording. I like here that you've mentioned drawing two diagrams. Again, the tension links them and the acceleration is not zero, but you can still use the diagrams to get expressions for Fnet... Fnet just isn't zero.

 

[baba89]

I would approach this problem by first drawing a free body diagram for both the helicopter and the frame. The helicopter experiences a lift force from the air, which is equal to its weight plus the weight of the frame. The second law of motion states that the net force on an object is equal to its mass times its acceleration. Therefore, we can calculate the lift force by multiplying the total mass of the helicopter and frame by the acceleration of the helicopter.

Next, we can use the same equation to calculate the tension in the cable that connects the frame to the helicopter. The tension in the cable is equal to the mass of the frame multiplied by the acceleration of the helicopter, plus the weight of the frame. This will give us the force that the cable exerts on the frame.

Finally, the force that the cable exerts on the helicopter can be calculated by subtracting the lift force from the force exerted by the cable on the frame. This will give us the net force acting on the helicopter, which is equal to its mass times its acceleration. This net force is the result of the helicopter accelerating while lifting the frame.

In terms of the "helicopter rotors", this refers to the spinning blades on top of the helicopter that generate lift. The lift force exerted by the air on the rotors is what allows the helicopter to lift off the ground. By accelerating upwards, the helicopter is increasing the lift force generated by the rotors, which in turn allows it to lift the frame as well.