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Upstream/Downstream
Entirely dependent on where the current is headed
Lets say it goes
[West]
Downstream follows the
current
Upstream opposes the
current
Inertial Reference Frames
We all motion our Is doing
For example, if the earth was our ,
Reference Frame
Inertial Reference Frame
ignore
we would ignore its movement and rotation.
It is strictly a position in space now
Make Wind Vectors
You only care about where the wind is
headed
Case 1 - Destination Provided
20m/s Wind is blowing from [Ottawa] to
[Toronto]
Its going to Toronto
20m/s[Toronto]
Case 2 - Origin Provided
45m/s Wind is blowing from [S60 W]
o
60
The destination it is headed to will be
colinear
The colinear direction would be
[N60 E]
o
45m/s[N60 E]
o
Make Wind Vectors
Resultant Vectors
If you have 2 vectors in non-parallel directions. You must find the
Example
Plane heads Wind blows
o
400m/s [EAST]
100m/s [N45 W]
45
Find with parallelogram method
45
resultant
v
p
g
=
v
p
w
resultant
v
w
g
v
p
wx
= 400
v
p
wy
= 0
v
w
gx
= -100cos(45) = -70.71
v
w
gy
= 100sin(45) = 70.71
v
p
gx
=
400
- 70.71
=
329.29
v
p
gy
=
0
70.71
=
70.71
70.71
329.29
336.8
77.88
336.8m/s [N77.88 E]
o
A golfer wants to hit a ball so that it lands
250m
away (on a horizontal plane).
If the golfer can strike the ball at
60m/s
, at what angle(s) should he strike the ball?
θ
60m/s
250m
v
x
=
v
y
60sin(θ)
θ
v
x
v
y
60m/s
t =
v
y
4.9
4.9
60sin(θ)
=
d =
v
x
(t)
=
250
=
60cos(θ)
60cos(θ)
4.9
60sin(θ)
( )
=
250
60cos(θ)
4.9
60sin(θ)
=
1225
3600cos(θ)sin(θ)
=
1800sin(2θ)
1225
0.6806 = sin(2θ)
C
A
S
T
There will be 2 angles sine will be positive
2θ = 42.88
2θ = 180 - 42.88
= 137.12
θ = 21.44
θ = 68.59