How to calculate impact speed of a wrecking ball? So I want to calculate the impact speed of a wrecking ball. I know that I can do that using potential and kinetic energy and the height it was swung from... but that does not account for the air resistance. I found some tutorials for how to calculate speed of free falling object, but the ball is moving on a curve held by the rope...
Can anybody help me with this please?
(And I'm sorry for my english)
 A: @zhutchens is correct. The drag force experienced by a wrecking ball traveling at a speed of ~tens of meters a second through air will be negligible compared to the force of gravity, and can safely be ignored in the analysis you describe. Equating the potential and kinetic energies is indeed a quick and convenient way to solve for the velocity of the ball at the bottom of its swing.
A: As mentioned before by two people, if you want to for practical applications you can assume that the drag force is negligible. Should you really want to calculate the drag force then you can do so. The thing is you would calculate it the same way as a free-falling object. Why?
Well (air)-drag is not direction dependent, it depends on the speed (along the curvature of the circle described by the chain and pivot); it depends on the shape of the face of the object (luckily a sphere makes this easy as it's the same shape in every direction); the viscosity and the density of the fluid (air in this case); and the surface area of the face (for a sphere this is the cross-section, so the area of a circle).
Meaning that if you could calculate drag force if it was free-falling than you could also do so if it's on a pendulum.
