Physics
posted by Tory .
A 63 kg canoeist stands in the middle of her 19 kg canoe. The canoe is 3.0 m long, and the end that is closest to land is 2.5 m from the shore. The canoeist now walks toward the shore until she comes to the end of the canoe.
a. When the canoeist stops at the end of her canoe, is her distance from the shore equal to, greater than, or less than 2.5 m?
b. Verify your answer to part (a) by calculating the distance from the canoeist to shore.

The center of gravity of the system will not move (ignoring water resistance).
It remains 2.5 + 3/2 = 4 m from shore
The canoe, being lighter, moves back more than the canoeist moves forward.
Call final distance of person from shore x
total mass = 63+19 = 82 kg
82 kg * 4 m = 328 kg m
so
328 = 63 x + 19 (x+1.5)
328 = 63 x + 19 x + 28.5
299.5 = 82 x
x = 3.65 m
This is not news to those of use who fool around in small boats. 
HOU VAN JULLIE