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Problem 3 (Lift and Drag Problems) Answer the following questions regarding lift and drag: a. Consider...


Problem 3 (Lift and Drag Problems) 

Answer the following questions regarding lift and drag:

 a. Consider the motion of a kayak on a relatively still lake: 

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From a fluid mechanics perspective, this presents an interesting situation since the kayaker is moving through two different fluids (air and water), both of which will impart a drag force on the kayak. The bottom of the kayak is relatively streamlined, with a drag coefficient of 0.03. while the top of the kayak (which includes the person has a larger drag coefficient of 0.25. Since the bottom of the kayak is relatively streamlined, we will use the total surface area in determining the drag force, which we will take to be 2.25 m². The top of the kayak is a blunt body, so we will use its frontal area of 0.95 m2. Determine the terminal speed of the kayak, if the person can output 120 Watts worth of power in rowing the kayak. Assume the water has a density of Pwater = 1000 kg/m and the air has a density of Pair = 1.225 kg/m3. 


Ans: 3.54 m/s

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Answer #1

Here two different drag forces are in action.

One due to water and other due to air.

So final net force is a sum of these two drag forces.

So u get velocity of kayak as 3.54 m/s.

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> hello,
I great working and easy to understand. I have a question, isn't that 3.54m/s the cube value of the velocity? because as i can see in the final equation we had V^3.

Shimo Thu, Jan 6, 2022 2:21 PM

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