document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=191944>Question 191944</A>This question is from textbook <A HREF=http://www.amazon.com/exec/obidos/ASIN/9780073533490/algebrahomeworkh>Elementary and Intermediate Algebra</A><BR>\n" );
document.write( ": <I><SPAN STYLE=\"word-break: break-all;\"> 106. Pole vaulting. In 1981 Vladimir Poliakov (USSR)<BR>\n" );
document.write( "set a world record of 19 ft 3/4<BR>\n" );
document.write( "in. for the pole vault<BR>\n" );
document.write( "(www.polevault.com). To reach that height, Poliakov<BR>\n" );
document.write( "obtained a speed of approximately 36 feet per second on<BR>\n" );
document.write( "the runway. The formula h _ _16t2 _ 36t gives his<BR>\n" );
document.write( "height t seconds after leaving the ground.<BR>\n" );
document.write( "a) Use the formula to find the exact values of t for which<BR>\n" );
document.write( "his height was 18 feet.<BR>\n" );
document.write( "b) Use the accompanying graph to estimate the value of t<BR>\n" );
document.write( "for which he was at his maximum height.<BR>\n" );
document.write( "c) Approximately how long was he in the air?\r<BR>\n" );
document.write( "\n" );
document.write( " </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #144063 by </B><A HREF=/tutors/aboutme.mpl?userid=Alan3354><B>Alan3354(69443)</B></A><img src=\"/images/stars/stars-13.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=Alan3354><IMG SRC=http://www.algebra.com/images/aboutme-small.gif BORDER=0 alt=\"About Me\" VALIGN=MIDDLE></A>&nbsp;<IMG SRC=http://www.algebra.com/cgi-bin/show-face.mpl?user=Alan3354><BR>You can <A HREF=\"/cgi-bin/embed-solution.mpl?show=1&solution=144063\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> Pole vaulting. In 1981 Vladimir Poliakov (USSR)<BR>\n" );
document.write( "set a world record of 19 ft 3/4<BR>\n" );
document.write( "in. for the pole vault<BR>\n" );
document.write( "(www.polevault.com). To reach that height, Poliakov<BR>\n" );
document.write( "obtained a speed of approximately 36 feet per second on<BR>\n" );
document.write( "the runway. The formula h _ _16t2 _ 36t gives his<BR>\n" );
document.write( "height t seconds after leaving the ground.<BR>\n" );
document.write( "h = -16t^2 + 36t<BR>\n" );
document.write( "a) Use the formula to find the exact values of t for which<BR>\n" );
document.write( "his height was 18 feet.<BR>\n" );
document.write( "18 = -16t^2 + 36t<BR>\n" );
document.write( "8t^2 - 18t + 9 = 0<BR>\n" );
document.write( "t = 0.75 seconds (going up)<BR>\n" );
document.write( "t = 1.5 seconds (coming down)<BR>\n" );
document.write( "t found using quadratic equation.  If you have questions, email me via the thank you note.<BR>\n" );
document.write( "b) Use the accompanying graph to estimate the value of t<BR>\n" );
document.write( "for which he was at his maximum height.<BR>\n" );
document.write( "I don't see a graph, but the easiest way to find max height is to get the average of the 2 values of t above.<BR>\n" );
document.write( "t = 1.125 seconds<BR>\n" );
document.write( "c) Approximately how long was he in the air? <BR>\n" );
document.write( "That would be 2 times the time at max height, or 2.25 seconds. </SPAN>\n" );
document.write( "</TD></TR></TABLE>\n" );