Position when 2 objects pass each other

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To find the height at which two objects pass each other, one thrown downward from 99m with an initial speed of 4 m/s and another propelled upward from the ground at 25 m/s, the equations of motion must be applied. The relevant equation is d = v1*t + (1/2)at^2, where d represents displacement, v1 is initial velocity, and a is acceleration due to gravity (9.8 m/s^2). By setting the displacement equations for both objects equal to each other, one can solve for time (t) and subsequently determine the height at which they meet. The discussion highlights the need for a clear starting point in solving the problem, emphasizing the importance of correctly applying the kinematic equations. Properly setting up the equations will lead to the solution for the height above ground where the two objects pass each other.
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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

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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Can you show exactly what you did?
 
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.
 
dvdqnoc said:
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...
 
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