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Two boxes are connected to each other. Box A (3.00 kg) lies on a table, the surface of...

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durbanville | High School Teacher | (Level 1) Educator Emeritus

Posted August 26, 2013 at 7:19 AM via web

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Two boxes are connected to each other. Box A (3.00 kg) lies on a table, the surface of which is frictionless and Box B (1.00 kg), connected by a pulley-system to Box A and suspended off the edge of the table, falls through a distance of 1.00m when the system is released.

What is the kinetic energy of Box B (in joules) just before it reaches the floor? Please explain your answer.

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justaguide | College Teacher | (Level 2) Distinguished Educator

Posted August 26, 2013 at 8:49 AM (Answer #1)

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Two boxes are connected to each other. Box A with mass 3 lies on a table, the surface of which is frictionless and Box B of mass 1 kg is connected by a pulley-system to Box A and suspended off the edge of the table. The box B falls through a distance of 1 m when the system is released.

The total energy of box B when it is suspended from a height of 1 m is (1/2)*m*v^2 + m*g*h = 0 + 1*1*9.8 = 9.8 J. When the system is released, the gravitational potential energy of the box is converted to kinetic energy. Just at the moment when the box touches the ground, all the potential energy has been converted to kinetic energy. The kinetic energy of the box is equal to 9.8 J.

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