TFS · Hydraulic & Fluid Applications · Problem 51PDFSolution in PDF ↓
TFS · Hydraulic & Fluid Applications · Problem 51
Problem & Solution
Video Synthesis
Topic: Hydraulic & Fluids Applications — A 4-inch aluminum sphere is dropped into a deep body of water.
Method: The coefficient of drag is 0.5.
Formula reference: formula that we need.
Key values: 170 pounds mass then I exert 170 pounds force on the ground and we sort of just use those interchangeably but really g over g c is lurking in the background making that all possible because that unit conversion is what allows us to switch between the two whereas in the UK or in parts of Europe or basically the rest of the world they have to say how many kilograms would be their mass or how many new ends would be their weight or the force that they are on the ground so they distinguish mass and weight and we gloss them over, 168 pound mass per cubic foot and then the volume of a sphere is given by 4 thirds pi r cubed and you should make sure you, 32.2 feet per second squared and then pretty quickly you reach terminal velocity where the drag force of the air upward is in equilibrium with the force of gravity down where and that
Reference: look up the density of aluminum so we can use the fact that mass eq
✅ Answer: B
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Student questions asked in live office hours about this problem
OH 80
Q: Why does the drag force equation use density divided by G_C instead of specific weight (gamma) like other fluid mechanics equations?
A: The drag force formula uses density rather than specific weight because that's what makes the units work out correctly in US customary units—when you multiply density, velocity squared, and area and divide by G_C, you get pound force. Using specific weight would introduce unwanted units. This is distinct from buoyancy, which fundamentally depends on specific weight due to the different physical phenomena generating these forces.