How to calculate change of velocity after hitting water?

  • Context: Undergrad 
  • Thread starter Thread starter Number1koer
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Discussion Overview

The discussion revolves around calculating the change in velocity when a diver hits the water, comparing different diving techniques such as a cannonball versus a normal dive. Participants explore the physics involved in the impact with water, including energy transfer and the factors affecting the resultant speed.

Discussion Character

  • Exploratory, Technical explanation, Conceptual clarification, Debate/contested

Main Points Raised

  • One participant suggests using video analysis to measure the distance moved between frames and the time elapsed to calculate average velocity.
  • Another participant questions the assumption that all kinetic energy is transferred to the water upon impact, prompting a discussion about remaining kinetic energy after hitting the water.
  • There is a request for a simple explanation of the factors affecting impact on water, including mass and velocity.
  • Some participants express curiosity about the energy dynamics involved in the impact, particularly regarding how much energy is actually transferred to the water.

Areas of Agreement / Disagreement

Participants exhibit disagreement regarding the energy transfer upon impact, with some asserting that not all kinetic energy is lost, while others question the basis for this claim. The discussion remains unresolved on these points.

Contextual Notes

Participants have not established specific assumptions or definitions regarding energy transfer or the mechanics of diving, which may affect the clarity of the discussion.

Number1koer
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Me and a Partner are presenting the physics of diving as our final in physics. He wants a ton of detail about the activity we choose so I thought it would be a good idea to show the difference from a cannonball vs a normal dive and the change in velocity that occurs with both, and also how much of your energy is transferred into the water. My partner is going to be filmed jumping off of a diving board, and I will then take the video and put it into logger pro. I am wondering if there is a fairly simple way to get the info I need. I am also wondering what info I will need, like if I will need her mass to calculate the change in velocity. If there isn't really a way to get exact numbers out of this, it would also be helpful for a simple explanation of what effects impact on water. (Mass, How velocity impacts it, etc.)
 
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Number1koer said:
it would also be helpful for a simple explanation of what effects impact on water. (Mass, How velocity impacts it, etc.)
What do YOU think effects the impact and the resultant speed in the water? You HAVE to show at least some effort if you want help on this forum.
 
Have you done video analysis of the motion of anything else? The basic idea is that you need to know how far she moves between video frames, and the time that elapses between video frames. The ratio is the average velocity. I just did a google search for video analysis of diver and got lots of hits with lots of details.
 
Number1koer said:
how much of your energy is transferred into the water
Why would the answer differ from "all of it"?
 
jbriggs444 said:
Why would the answer differ from "all of it"?
Wouldn’t you still have kinetic energy because you are still moving?
 
Number1koer said:
Wouldn’t you still have kinetic energy because you are still moving?
I usually stop before hitting the bottom of the pool.
 

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