fisica1-youn-e-freedman-exercicios-resolvidos

8.92: Since mass is proportional to weight, the given weights may be used in determining
velocities from conservation of momentum. Taking the positive direction to the left,
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(800 N)(5.00 m/s) cos 30.0 − (600 N)(7.00 m/s) cos 36.9
v =
= 0.105 m s
1000 N
8.93: a) From symmetry, the center of mass is on the vertical axis, a distance
( L 2)cos( α 2) from the apex. b) The center of mass is on the (vertical) axis of
symmetry, a distance 2(
L / 2) / 3 = L 3 from the center of the bottom of the . c) Using
the wire frame as a coordinate system, the coordinates of the center of mass are equal,
and each is equal to ( L 2) / 2 = L 4.
The distance of this point from the corner is
( 1 8) L = (0.353) L.
This may also be found from consideration of the situation of part
( a), with α = 45 ° d) By symmetry, the center of mass is in the center of the equilateral
triangle, a distance
( L 2)(tan60° ) = L 12 = (0.289)
L above the center of the base.
8.94: The trick here is to notice that the final configuration is the same as if the canoe
( assumed symmetrical) has been rotated about its center of mass. Intially, the center of
mass is a distance
(45.0 kg) (1.5 m)
(105 kg)
= 0.643 m from the center of the canoe, so in rotating about
this point the center of the canoe would move 2 × 0.643 m = 1.29 m.
8.95: Neglecting friction, the total momentum is zero, and your speed will be one-fifth of
the slab’s speed, or 0.40 m / s.