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Physics
Classical Physics
Mechanics
Calculating Windspeed after Brick Launch from Dumpster Lid
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[QUOTE="jrmichler, post: 6522412, member: 638574"] There are four main steps to solve this. #1: How much wind to catch the lid and flip it up. A similar problem is the loading on a roof overhang during a hurricane. The loading is the area of the overhang times the wind velocity pressure times 2.0. The uplift coefficient of an overhang is 2.0. You can calculate the force to lift the lid from the weight and dimensions of the lid plus the weight and location of the brick, or you can measure it directly with a spring scale. The result will be the minimum wind to lift the lid. The actual wind was likely greater than that. #2: The lid is up, and the wind force is accelerating it. This is an F = ma problem where the wind force is a function of lid position, and the wind velocity is unknown. Search [B]lift and drag on a flat plate[/B] to learn about wind forces as a function of lid position. This problem can be solved by a numerical simulation with different wind velocities. The goal is to calculate lid velocity vs time and lid velocity vs lid position for different wind speeds. #3: Now you have some curves of lid velocity vs time, and lid velocity vs position, you can calculate the brick velocity vs lid position. The brick initially moves with the lid. At some lid velocity and position, the brick starts to slide. The free body diagram of the brick includes the force of lid acceleration, gravity, and centrifugal force. At some point, the brick slides off the lid. Do this calculation for each wind velocity. This is a second numerical simulation problem. The goal is calculate the velocity, direction, and height at which the brick leaves the lid for different wind velocities. #4: When the brick left the lid, it had a velocity, direction, and height. All of those variables are a function of the wind velocity. It came to a stop at a distance and height. In between, it was subject the force of gravity plus the wind. This is a third numerical simulation problem. Or you can just say "It was blowing so hard it threw that brick 55 feet". [/QUOTE]
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Calculating Windspeed after Brick Launch from Dumpster Lid
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