document.write( "Question 1051153: An object is thrown straight up from the roof's edge of a 48-foot building at an initial velocity of 32 ft/s. How long will it take to reach the ground? \n" ); document.write( "

Algebra.Com's Answer #666737 by ikleyn(52831) $\"\"$ $\"About$

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\n" ); document.write( "An object is thrown straight up from the roof's edge of a 48-foot building at an initial velocity of 32 ft/s.
\n" ); document.write( "How long will it take to reach the ground?
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document.write( "The governing equation is \r\n" );
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document.write( "h(t) = -16t^2 + 32t + 48,\r\n" );
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document.write( "where t is the time after throwing, h(t) is the object height (elevation over the ground surface in feet, \r\n" );
document.write( "32 is the initial velocity in ft/s, 48 is the initial elevation, 16 =  a is the half of the value \r\n" );
document.write( "of the free fall acceleration in ft/s^2.\r\n" );
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document.write( "We need to find the value of t for which h(t) = 0,  or\r\n" );
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document.write( "-16t^2 + 32t + 48 = 0.\r\n" );
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document.write( "Divide both sides by (-16). You will get\r\n" );
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document.write( "t^2 - 2t - 3 = 0.\r\n" );
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document.write( "Factor the left side\r\n" );
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document.write( "(t-3)*(t+1) = 0.\r\n" );
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document.write( "The positive root t = 3 is the time we are seeking for.\r\n" );
document.write( "The other root is negative, so we ignore it.\r\n" );
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document.write( "Answer.  It will take 3 seconds for the onject to reach the ground.\r\n" );
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\n" ); document.write( "\n" ); document.write( "Plot y = $\"-16t%5E2+%2B+32t+%2B+48\"$ \r
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\n" ); document.write( "\n" ); document.write( "For more similar solved problems see the lessons\r
\n" ); document.write( "\n" ); document.write( "    - Problem on a projectile moving vertically up and down\r
\n" ); document.write( "\n" ); document.write( "    - Problem on an arrow shot vertically upward\r
\n" ); document.write( "\n" ); document.write( "    - Problem on a ball thrown vertically up from the top of a tower \r
\n" ); document.write( "\n" ); document.write( "    - Problem on a toy rocket launched vertically up from a tall platform\r
\n" ); document.write( "\n" ); document.write( "in this site.\r
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\n" ); document.write( "\n" ); document.write( "Also, you have this free of charge online textbook in ALGEBRA-I in this site\r
\n" ); document.write( "\n" ); document.write( "    - ALGEBRA-I - YOUR ONLINE TEXTBOOK.\r
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\n" ); document.write( "\n" ); document.write( "The referred lessons are the part of this textbook under the topic \"Projectiles launched/thrown and moving vertically up and dawn\".\r
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