<PRE><B>Question 118874</B>
If an object is given an initial velocity of v0 feet per second from a height of S0 feet, then its height S after t seconds is given by the formula S= -16t SQRD+vt+S . A rock is thrown into the air at 26 feet per second from a height of 13 feet. How long does it take to reach the earth?
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We can write it, the ground would be 0 ft;
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-16t^2 + 26t + 13 = 0
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Use the quadratic formula to solve this equation: a=-16; b=26; c=13
{{{t = (-b +- sqrt( b^2-4*a*c ))/(2*a) }}}
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{{{t = (-26 +- sqrt(26^2-4*-16*13 ))/(2*-16) }}}
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Do the math here.
you should get a positive solution of t = 2.026 sec to reach the ground
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Check your solution in the original equation  
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