<PRE><B>Question 30301</B>
PLEASE HELP ME A rocket is fired with an initial velocity of 800 meters per second. When will it be 32000 meters above the starting point? 
Than answer I got was : 40 second because I divided... I think its wrong thought 
AS THE ROCKET GOES UP AGAINST EARTHS GRAVITATIONAL FORCE , ITS VELOCITY REDUCES,GIVEN BY ACCELERATION DUE TO GRAVITY =-9.8 M/SEC^2..THE FORMULA TO BE USED IS 
S = UT + (G/2)T^2....WHERE 
U = INIYIAL VELOCITY = 800 M/SEC
T = TIME ELAPSED IN SECS.
G=ACCELERATION DUE TO GRAVITY = - 9.8 M/SEC^2 FOR UPWARD TRAVEL...SO..WE GET 
32000 = 800T -(9.8/2)T^2=800T-4.9 T^2
4.9T^2-800T+32000 =0
{{{t = (800 +- sqrt( 800^2-4*4.9*32000 ))/(2*4.9) }}} 
T=70.1 WHILE GOING UP AND 
T=93.2 WHILE FALLING DOWN.

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