Homework Help: math

Posted by ted on Wednesday, November 24, 2010 at 4:50pm.

A pair of skydivers jump out airplane 5.5km above the ground. The equation H=5500-5t^2 is an appropriate model for the divers' altitude in metres at tseconds after jumping out of the plane.
A. After 10secs how far have the divers fallen?
B. They open their chutes at an altitude of 1000metres. how long did they free-fall?
C. If a parachute does noe open at 1000metres,how much time is left to use the emergency chute?

For (a),I got H=5000 and (b), I got t=30secs
BUT i do not know how to get the answer for QUESTION (C).
PLS HELP ME ,HAVE TRIED IT BUT I DIDN'T GET IT.

math - Reiny, Wednesday, November 24, 2010 at 5:43pm
Find out how long it would take to fall the entire 5500 m
so
0 = 5500 - 5t^2
t^2 = 1100
t = 33.167 sec

but he has already fallen for 30 sec , so he has
3.167 sec left

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