document.write( "Question 1153996: Calvin weighs 70 pounds and is walking in the front door at a rate of 3 ft/s. He is tackled by Hobbes running in the opposite direction at 15 ft/s. If Hobbes weighs 120 lbs, what is the resultant speed of Calvin and Hobbes? \n" ); document.write( "

Algebra.Com's Answer #776351 by ikleyn(53764) $\"\"$ $\"About$

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document.write( "Since the problem asks about the resultant speed of both, it means that after collision, they move \r\n" );
document.write( "as one single body with the common speed.\r\n" );
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document.write( "    In Physics, such collision is called \"inelastic\" collision.\r\n" );
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document.write( "For such collisions, the Linear Moment conservation low is applicable:\r\n" );
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document.write( "     -  = .    (1)\r\n" );
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document.write( "In formula (1),  and  are their masses;   and  are their velocities before the collision;\r\n" );
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document.write( "the sum   is the total mass of the \"glued\" body and  is their common speed after collision.\r\n" );
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document.write( "The sign \" - \" in formula (1) says that the bodies move initially in opposite directions.\r\n" );
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document.write( "The sign of the sum in the left side of (1) determine the direction, in which the resulting mass does move.\r\n" );
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document.write( "Substitute the given data into the formula (1)\r\n" );
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document.write( "    70*3 - 120*5 = (70+120)*V\r\n" );
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document.write( "and get\r\n" );
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document.write( "    V =  = -2.053.\r\n" );
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document.write( "ANSWER.  The resulting speed is -2.053 ft/s.  They move together in the same direction, as Hobbes moved before the collision.\r\n" );
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\n" ); document.write( "\n" ); document.write( "It is a typical Physics problem on inelastic collisions,\r
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