Posted by Michael on Tuesday, April 6, 2010 at 1:27am.
A projectile is shot straight up from the earth's surface at a speed of 1.20×104 KM/HR.
How high does it go?

Physics  drwls, Tuesday, April 6, 2010 at 1:35am
Follow the steps explained in my previous answer.
http://www.jiskha.com/display.cgi?id=1270449424
If you are just looking for numbers to put into a test or homework, rather than an understanding of how the problem is done, then you have come to the wrong place. 
Physics  echem, Tuesday, April 6, 2010 at 1:40am
First need to convert km/hr to meters/second
(I got around 3333.33 m/s but you might want to double check that)
so 3333.33 is your initial velocity v_i
using kinematics equation:
v_f=V_i+at
y=v_i*t+(1/2)at^(2)
the highest point the projectile reaches is when v_f is zero
so solve for time using the first equation and the known variables
a= 9.8 m/s^2
v_i= 3333.33 m/s
use the time you determined and plug it into the second kinematics equation and then you'll get your max height. 
Physics  drwls, Tuesday, April 6, 2010 at 1:48am
The method described above will not give the correct answer because g is not constant over the large altitude range that the projectile will travel.
Refer to http://www.jiskha.com/display.cgi?id=1270449424 
Physics  echem, Tuesday, April 6, 2010 at 1:56am
That's interesting...because the altitude is so high you have to deal with escape velocity instead of the usual kinematics.