Pelican Dive: Calculating Escape Height for Fish

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SUMMARY

The discussion focuses on calculating the minimum height at which a fish must spot a pelican diving from 20.0 meters to evade capture. The pelican's free-fall acceleration is approximated at 10 m/s² for simplicity. By determining the time it takes for the pelican to reach the water and accounting for the fish's 0.15 seconds of evasive action, participants concluded that the fish must spot the pelican at a minimum height of approximately 2.8875 meters to ensure its safety. The final verified answer was 2.86 meters when using the more precise acceleration of 9.8 m/s².

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  • Basic knowledge of time calculation in physics
  • Ability to perform unit conversions and approximations in physics problems
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  • Study kinematic equations in detail, focusing on free-fall scenarios
  • Learn about the effects of acceleration due to gravity on falling objects
  • Explore real-world applications of physics in animal behavior and evasion tactics
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This discussion is beneficial for students studying physics, particularly those focusing on kinematics, as well as educators looking for practical examples of physics concepts in action.

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Pelicans tuck their wings and free-fall straight down when diving for fish. Suppose a pelican starts its dive from a height of 20.0 m and cannot change its path once committed.If it takes a fish 0.15 s to perform evasive action, at what minimum height must it spot the pelican to escape? Assume the fish is at the surface of the water.
 
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Homeworkboy,
I am a bit rusty with these types of problems, but i believe that i have it.

Where you would start, is to find out how long it would take the pelican to get to the water, regardless of fish.

change in X=20m
acceleration=freefall, or 10m/s2 (its 9.8 to be exact, but im' just using 10)
time=?
starting Velocity=0

so change in X=volt+.5At2

so, you get the time it takes the pelican to reach the water by solving that. Now since the fish can evade in .15 seconds, take the time yu found in the previous problem and subtract .15 from it. This will give you the time that it takes for the pelican to get to .15 seconds away.

Now that you have the time it takes for the pelican to get within evading distance, plug THIS time back into the change in position equation to get the distance from the fish the pelican can be with the fish still being safe.

I would like you to go back through and do the steps, but to check your answer, the answer that i ended up with is 2.8875m.

Good luck in physics!
 
Hey thanks a million! i perfectly understood it...i worked it out the way u said and it came upto 2.86 (since i used 9.8m/s2)...so i checked it and it was the right answer..thanks a lot..
 

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