SOLUTION: AN OBJECT IS PROJECTED UPWARD FROM THE TOP OF A TOWER. ITS DISTANCE IN FEET ABOVE THE GROUND AFTER t SECONDS IS GIVEN BY s(t)=-16t2+64t+80. HOW MANY SECONDS WILL IT TAKE TO REACH

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Question 62553: AN OBJECT IS PROJECTED UPWARD FROM THE TOP OF A TOWER. ITS DISTANCE IN FEET ABOVE THE GROUND AFTER t SECONDS IS GIVEN BY s(t)=-16t2+64t+80. HOW MANY SECONDS WILL IT TAKE TO REACH THE GROUND?
Answer by funmath(2933) About Me  (Show Source):
You can put this solution on YOUR website!
AN OBJECT IS PROJECTED UPWARD FROM THE TOP OF A TOWER. ITS DISTANCE IN FEET ABOVE THE GROUND AFTER t SECONDS IS GIVEN BY s(t)=-16t^2+64t+80. HOW MANY SECONDS WILL IT TAKE TO REACH THE GROUND?
s(t)=0 when the object is on the ground, so set the problem = 0 factor and solve.
0=-16t%5E2%2B64t%2B80
0=-16%28t%5E2-4t-5%29
0%2F-16=-16%28t%5E2-4t-5%29%2F-16
0=t%5E2-4t-5
0=%28t-5%29%28t%2B1%29
t-5=0 and t+1=0
t=5 and t=-1
ignore the negative value it it's not pertinent.
t=5 s for the object to hit the ground.
Happy Calculating!!!!