need help solving this fluids problem! You and a friend decide to get kicked out
ID: 1863376 • Letter: N
Question
need help solving this fluids problem!
You and a friend decide to get kicked out of school while performing an experiment in fluid mechanics. With a fire hose, a trash can lid, and a Hat board you race from one side of Riverside Hall to the other. Assume the hose has an exit velocity of 19 m/s and diameter of 0.06 m and the splash has equal area as the hose. Assuming the chair with a person has a resistance to sliding floor of 200 N and a mass of 100 kg. Which chair will win in a race? Give the order from first to last place. (4 pts) Compute the force on chair III and initial acceleration when the chair is at rest. (8 pts) Compute the maximum velocity of the chair II and person. (8 pts)Explanation / Answer
a)
I will win because it is deflecting the jet by the maximum amout (90+20 degrees)
Since deflection equals force, it will be pushed the most
b)
Initial Force = rate of change of momentum of chair
= rate of change of momentum of jet - 200
= flow rate x delta v - 200
= density x v x A x v (1-cos 90) - 200
= 820.7 N
Initial accn = 8.2 m/s2
c)
At the maximum velocity, accn must be 0
i.e. rate of change of momentum of jet = 200
density x (Relative velocity)^2 x A (1-cos 70) = 200
Relative velocity = 10.37 m/s = 19 - speed of chair
Speed of chair = 8.632 m/s
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