12) Water flows through a horizontal pipe of cross-sectional area 10.0 cm2 at a pressure of 0.250 atm with a flow rate is 1.00 L
/s. At a valve, the effective cross-sectional area of the pipe is reduced to 5.00 cm2. What is the pressure at the valve? The density of water is 1000 kg/m3, and treat it as an ideal incompressible fluid
1 answer:
Answer:
The pressure after passing the valve is 23,8 [Kpa] ( 0,234 atm) and the pressure drop is about 1,53 [Kpa]
Explanation:
We need to use the formula of bernoulli, in the attached image we can see the fluid throw the pipe, we also can calculate the velocity inside the pipe using the flow rate and the cross sectional area.
For this case, we don't use the elevation difference and therefore those terms can be cancelled.
When the area has reduced the velocity of the fluid is increased but there is a drop pressure through the valve.
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Answer:
0.767
Explanation:
The work done on the truck by the frictional drag force is given by
where
F is the magnitude of the frictional force
d = 38.0 m is the maximum displacement allowed for the truck
The negative sign is due to the fact that the force of friction is opposite to the motion of the truck
The force of friction can also be written as:
where
is the coefficient of kinetic friction between the truck and the lane
m is the mass of the truck
g is the acceleration of gravity
So we can rewrite the work done as
(1)
According to the work-energy theorem, the work done by friction is equal to the change in kinetic energy of the truck:
(2)
where
v = 0 is the final velocity of the truck
u = 23.9 m/s is the initial velocity of the truck
By combining (1) and (2) we get
And solving for , we find the minimum coefficient of kinetic friction able to stop the truck in a distance d: