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Position when 2 objects pass each other

  • Thread starter dvdqnoc
  • Start date
  • #1
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Homework Statement


An object is thrown downward with an initial speed of 4 m/s from a height of 99m above the ground. At the same instant, a second object is propelled vertically from the ground level with a speed of 25 m/s.
The acceleration of gravity is 9.8 m/s^2.
At what height above the ground will the two objects pass each other? Answer in units of m.


Homework Equations


http://www.glenbrook.k12.il.us/gbssci/phys/Class/1DKin/U1L6a1.gif [Broken]

The Attempt at a Solution


Well I tried to find a common variable to plug in. I tried to plug in the position, then find time, then find the position, but it didnt work. Any help is appreciated.
 
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Answers and Replies

  • #2
learningphysics
Homework Helper
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Can you show exactly what you did?
 
  • #3
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What I did didn't work. I kind just mushed stuff together. I might as well have said "I didnt know where to start" because I didnt.
 
  • #4
learningphysics
Homework Helper
4,099
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What I did didn't work. I kind just mushed stuff together. I might as well have said "I didnt know where to start" because I didnt.
the equation to use is:

d = v1*t + (1/2)at^2

now use d = X - Xo

X - Xo = v1*t + (1/2)at^2

so: X = Xo + v1*t + (1/2)at^2

X is the height at any time t. Xo is the initial height.

use this to get the displacement equations for each of the 2 objects...

after you do that, set them equal... solve for t...
 
Last edited:

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