Need help with kinetic energy calculation

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SUMMARY

The discussion focuses on calculating the kinetic energy (KE) of a person weighing 80 kg who falls from a height of 8 meters, specifically after falling 2 meters. The correct approach involves using the conservation of energy principle, where the potential energy (PE) lost during the fall translates into kinetic energy. The correct formula for kinetic energy is KE = 1/2 * m * v^2, where the velocity must be determined based on the height fallen. The initial calculation of 3841.6 joules is incorrect due to a misunderstanding of the velocity at that point in the fall.

PREREQUISITES
  • Understanding of basic physics concepts such as kinetic energy and potential energy
  • Familiarity with the equations of motion and energy conservation
  • Ability to perform calculations involving mass, height, and gravitational acceleration
  • Knowledge of the formula KE = 1/2 * m * v^2
NEXT STEPS
  • Study the principles of conservation of energy in physics
  • Learn how to calculate potential energy using PE = m * g * h
  • Explore the relationship between height fallen and velocity using kinematic equations
  • Practice problems involving kinetic energy calculations in various scenarios
USEFUL FOR

This discussion is beneficial for physics students, educators, and anyone interested in understanding the calculations related to kinetic and potential energy in motion scenarios.

Warren
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Hi

This seems like a helpful community so I thought I could ask you guys for some help.

First of all I need to clarify that English is not my first language so you'll have to excuse me if I make any grammatical or spelling errors.

Ok, here's my question:

I'm am trying to calculate the kinetic energy of a person who is standing on a diving board 8 meters above the surface. He weighs 80kgs.

What is his kinetic energy after falling 2m ?

I think it's 1/2*80*9,8^2 = 3841,6 joule

But the textbook tells me I have the wrong answer

I also have to find out his velocity as he reaches the surface, and I have no clue where to even begin.

Any help would be appreciated, thank you.
 
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You appear to have used the ke equation, without knowing his velocity - where did you get 9'8 from??

This is about conservation of energy.

Calculate how much PE he loses in falling 2m.

This is the ke he has after 2 metres.

For the speed as he hits the water, calculate how much PE he has lost by this point, this gives you the KE. Work backwords to find the velocity.
 

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