Homework Help: Velocity of ball problem

1. Feb 13, 2008

princesspriya

1. The problem statement, all variables and given/known data
ball is thrown upward from the ground with an initial speed of 25m/s; at the same instant a ball is dropped from rest from a building 15m high. After how long will the balls be at the same height?

2. Relevant equations

3. The attempt at a solution
well the first ball has initial(vi) of 25m/s and if its thrown that at its peak it wud be 0m/s and the acceleration is -9.81 and i used vf=vi+at which will give me 2.55
and for the second ball the initial velocity is 0 so i used x=1/2a(t)^2 and i got 1.75

i have no clue like what to do after you get both the times like how do u find where they would meet up??

thx for hte help

2. Feb 13, 2008

Hootenanny

Staff Emeritus
So you have two [kinematic] equations with two unknowns, how would you normally solve a system of simultaneous equations?

3. Feb 13, 2008

kamerling

give an expression for the heigth of the ball as a function of time and then set them equal, and then solve for t.

in general you have y(t) = y(0) + v(0)t - 1/2gt^2 for an object released at time t=0 at height y(0) with initial speed v(0). you know y(0) and b(0) for both balls.