Homework Help Forum: physics

Posted by Brian on Friday, November 6, 2009 at 4:19pm.

Ricardo, mass 88 kg and Carmelita, who is lighter, are enjoying Lake Merced at dusk in a 30 kg canoe. When the canoe is at rest in the placid water, they exchange seats, which are 3.0 m apart and symmetrically located with respect to the center of the canoe. Ricardo notices that the canoe moved 63.5 cm relative to a submerged log during the exchange and calculates Carmelita's mass, which she has not told him. What is it?

• physics - MathMate, Friday, November 6, 2009 at 8:50pm

  mr..........|..............mc mc..............|..........mr The vertical bar | represents the centre of gravity of the masses of the two persons, mr for Ricardo, and mc for Carmelita. When they exchange seats, they exert a force on the canoe in such a way that the heavier person pushes more on the canoe. The centre-of gravity (in theory) remains at the same place. Therefore (3 - 0.635)/2=1.1825 is the location of centre of gravity from Ricardo. We have therefore: mr*1.1825=mc*(3-1.8175) mc=mr*1.1825/1.8175 =57.25 kg Check my thinking.

  
  

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