Mechanical energy- Falling rock

  • Thread starter fiziks09
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  • #1
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Homework Statement


If the original height of a falling rock is y1 = h = 3.0m; calculate the rock's speed just before it hits ground.


Homework Equations


From conservation of mechanical energy law

1/2mv1^2 + mgy1 = 1/2mv2^2 + mgy2

The Attempt at a Solution


I think i'm supposed to find v2 i.e final velocity

v1 = 0 (from rest)
y1 = 3
Applying the formula stated above we find that the m's cancel out giving

v2 = sqrt(2g(y2 - y1))
= sqrt(2 x 9.8(3 - 0))
= sqrt(58.8)
= 7.7m/s

Please i want to know if my solution is correct. I'm not sure if it is right to take y2 as zero. Any help will be very much appreciated
 

Answers and Replies

  • #2
Doc Al
Mentor
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Perfectly done!
 
  • #3
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Okay; thanks for verifying !!!
 

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