A boat whose speed in still water is 3.70 m/s must aim upstream at an angle of 29.5°(with respect to a line perpendicular to the shore) in order to travel directly across the stream. (a) What is the speed of the river’s current?(1.82m/s)(b) What is the resultant speed of the boat with respect to the shore?(3.22m/s)
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v
Bw
is the velocity of the boat with respect to the water
v
Ws
is the velocity of the water with respect to the shore
v
Bs
is the velocity of the boat with respect to the shore
a
)
sin
v
Ws
v
Bw
v
Ws
v
Bw
sin
3.70 m/s
sin29.5
1.82 m/s
b
)
v
Bs
v
Bw
cos
3.70 m/s
scos29.5
3.22 m/s
v
Ws
v
Bw
v
Bs
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NEWTON’S SECOND LAW
•
The acceleration of an object is directly
proportional to the net force acting on it and
is inversely proportional to its mass.
The
direction of the acceleration is the direction
of the net force acting on the object.
F
ma
x
x
y
y
z
z
F
ma
F
ma
F
ma
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