Calculating Impact Speed of 4.00kg Cannon Ball Dropped from 55.0m

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Homework Help Overview

The problem involves calculating the impact speed of a 4.00 kg cannon ball dropped from a height of 55.0 m, using principles of energy conservation while assuming negligible air resistance.

Discussion Character

  • Exploratory, Conceptual clarification, Mathematical reasoning

Approaches and Questions Raised

  • The original poster expresses confusion regarding the application of energy conservation principles. Some participants suggest relating gravitational potential energy to kinetic energy, while others provide equations and methods for solving the problem.

Discussion Status

Participants are exploring different approaches to the problem, with some providing detailed calculations and others offering simplified equations. There is no explicit consensus on a single method, but multiple interpretations and calculations are being discussed.

Contextual Notes

Participants are working under the assumption of negligible air resistance and are discussing the implications of energy conservation in this context.

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Homework Statement


Using energy conservation and assuming negligible air resistance, calculate the impact speed of a 4.00 kg cannon ball after being dropped from a height of 55.0 m.



Homework Equations


KE sub total=KE sub 1+KE sub 2
speed=distance/time
gravity=9.8


The Attempt at a Solution


I'm completely lost as to how to get this with energy conservation. Can someone please help?
 
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Welcome to the physics forums! Hope you ask lots of questions here.

As the ball drops, its gravitational potential energy is converted to kinetic energy. Start with:
Potential energy at the top = kinetic energy at the bottom

Fill in the detailed formulas, solve for the quantity you want to find, then put in the numbers you know.
 
Thank you!

TE=KE+PE sub g
PE sub g=mgh
PE sub g=4*9.8*55=2200 J
KE=0
TE=0+2200
2200=KE+0
KE=2200=1/2*4*v^2
4400=4*v^2
1100=v^2
v=33 m/s
 
That's it!
Maybe simpler to write mgh = 1/2m*v^2, cancel the m's, then solve for v:
v = sqrt(2gh) = sqrt(2*g*55) = 32.8 m/s
 

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