Jim Guinn’s PHYS2211 Assignment #18
Due Wed., Apr. 21, 2010
1.
A garden hose has an intake opening of approximately 4.00cm
2
.
The other end of the
hose is attached to a sprinkler with a total output area of about 0.500cm
2
.
As the water leaves
the sprinkler it goes straight up into the air to a height of 3.50m before coming back down.
What is the speed of the water at the intake end of the hose?
If the water at the sprinkler end of the hose goes up to a height of 3.50m we can use that
to determine the initial speed of the water as it leaves the sprinkler.
With
v
2
= v
o
2
+ 2a
∆
x ,
0 = v
o
2
+ 2 (9.80m/s
2
) (3.50m) , or
v
o
2
= 68.6m
2
/s
2
, so
v
o
= 8.28m/s .
Now using the continuity equation we have
A
1
v
1
= A
2
v
2
, or
v
1
= A
2
v
2
/ A
1
= (0.500cm
2
) (8.28m/s) / (4.00cm
2
) , so
v
1
= 1.04m/s .
2.
Approximate the shape of an airfoil with the triangular shape shown.
The bottom side is
2.00m long and the triangle is 30.0cm high.
Determine the difference in pressure from the top
of the triangle to the bottom if air is flowing along the bottom of the triangle at a speed of
600.km/hr at a pressure of 1.00atm and density of 1.2kg/m
3
.
(Hint: air flowing over the top has
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 Spring '11
 lomant
 total output area

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