Aircraft Carrier Forces on Impact

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Discussion Overview

The discussion revolves around calculating the forces experienced by an aircraft when its jump cable catches to stop it on an aircraft carrier. The aircraft is traveling at 110 mph, and various conditions regarding its weight distribution and height are provided. Participants explore dynamics involving momentum and kinetic energy, while also considering the implications of the cable's elasticity.

Discussion Character

  • Technical explanation
  • Debate/contested
  • Homework-related

Main Points Raised

  • One participant seeks assistance in calculating the impact force on the aircraft, emphasizing the need to consider gravity and the non-elastic nature of the cable.
  • Another participant challenges the assumption of a non-elastic cable, arguing that it is unrealistic and suggesting that the main force felt would be the acceleration force from the cable stopping the plane.
  • A participant reiterates the initial request for help, expressing frustration over the lack of progress and urging others to provide more detailed thoughts.
  • One participant clarifies that they are specifically interested in the vertical force on the front axle due to rapid downward rotation, questioning how to approach the problem without assuming a rigid cable.
  • Another participant comments on the nature of the problem, suggesting that the basic equations being used may not be appropriate for this scenario.

Areas of Agreement / Disagreement

Participants express differing views on the assumptions regarding the cable's elasticity, with some arguing that a non-elastic model is not useful, while others maintain that it is a critical aspect of the problem. The discussion remains unresolved, with no consensus on the best approach to calculate the forces involved.

Contextual Notes

Participants highlight limitations in the assumptions made, particularly regarding the cable's elasticity and the applicability of basic equations to the problem. There is also uncertainty about how to accurately account for the forces acting on the aircraft during the impact.

codywookman
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I need help finding the forces when an aircraft’s jump cable catches to stop a plane on an aircraft carrier ship. The aircraft is traveling at 110 mph with the front of the plane 3 feet off the deck of the ship. If the assumption is made that the cable stops the aircraft immediately (the cable is not elastic), what would be the estimated impact force on the front end of the aircraft with the following conditions?
-The aircraft is 24 feet long
-1000 lbs located 4 feet above rear axle (pivot point)
-5000 lbs located 5 feet above center of plant (when plane is level)
-1500 lbs located 3 feet above front axle
-Do NOT ignore gravity
-Assume no impact absorbed by the front tire

I think it involves dynamics with momentum, kinetic energy, and maybe more.
L (linear momentum) = mass * velocity
A (angular momentum) = L x r (cross product of linear momentum and vector)

Tried using angular momentum (lb ft2 / sec) but that will not add with gravitational force multiplied by distance and mass (lb ft2 / s2). I'm really stuck here please help get me started!
 
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The assumption that the cable is not elastic (or on a spool with a brake) is so far from reality that I don't see how it is a useful constraint to the problem. Aside from a momentary impact force of the wheels hitting the carrier (then the continuous force of its weight), the main force felt is the acceleration force of the cable stopping the plane via f=ma.
 
codywookman said:
I need help finding the forces when an aircraft’s jump cable catches to stop a plane on an aircraft carrier ship. The aircraft is traveling at 110 mph with the front of the plane 3 feet off the deck of the ship. If the assumption is made that the cable stops the aircraft immediately (the cable is not elastic), what would be the estimated impact force on the front end of the aircraft with the following conditions?
-The aircraft is 24 feet long
-1000 lbs located 4 feet above rear axle (pivot point)
-5000 lbs located 5 feet above center of plant (when plane is level)
-1500 lbs located 3 feet above front axle
-Do NOT ignore gravity
-Assume no impact absorbed by the front tire

I think it involves dynamics with momentum, kinetic energy, and maybe more.
L (linear momentum) = mass * velocity
A (angular momentum) = L x r (cross product of linear momentum and vector)

Tried using angular momentum (lb ft2 / sec) but that will not add with gravitational force multiplied by distance and mass (lb ft2 / s2). I'm really stuck here please help get me started!

I really see no attempt on solving this problem on your end. Please provide more work and thoughts.
 
russ_watters said:
The assumption that the cable is not elastic (or on a spool with a brake) is so far from reality that I don't see how it is a useful constraint to the problem. Aside from a momentary impact force of the wheels hitting the carrier (then the continuous force of its weight), the main force felt is the acceleration force of the cable stopping the plane via f=ma.

I guess I forgot to write in the problem that the only force we are looking for is the vertical force exerted on the front axle of the plane due to it rotating downward so quickly. I misjudged the effect that the cable would contribute so much more to this effect if it were rigid instead of elastic. Any ideas how to solve it without assuming that for the cable?
 
codywookman said:
I guess I forgot to write in the problem that the only force we are looking for is the vertical force exerted on the front axle of the plane due to it rotating downward so quickly. I misjudged the effect that the cable would contribute so much more to this effect if it were rigid instead of elastic. Any ideas how to solve it without assuming that for the cable?

Is this a homework problem, or something your just trying to solve. This isn't the kind of problem you use the basic equations you're trying to use. You're not even going to be close.
 

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