terminal velocity

Speed of a rising drop of oil

The oil spill is still in the news (sadly). One thing that keeps coming up is the speed that the oil bubbles rise to the surface. This is important in different oil-capture methods. The common statement is that smaller bubbles of oil can take quite a long time to reach the surface and larger bubbles can take about 2 days. This is one of those cases where things do not scale quite the same. Suppose there is a spherical oil bubble rising at a constant speed. Here is a force diagram for such a bubble: If this drop is going at a constant speed, then all these forces have to add up to the…

Star Trek Space Jump

While I am still fresh on the Space Jump topic, let me take it to the extreme. Star Trek extreme. SPOILER ALERT But really, is this a spoiler alert if it is from the trailer of a movie that has been out forever? Of course, I talking about the latest Star Trek movie where three guys jump out of a shuttle and into the atmosphere. So, in light of the Red Bull Stratos jump, how would this jump compare? First, my assumptions: This Star Trek jump is on the planet Vulcan. I am going to assume this is just like Earth in terms of gravity and density of air. The jumpers in Star Trek have on stuff…

Stratos Jump for Mere Mortals

Crazy, but I was on CNN Saturday night. They contacted me at the last minute to talk about the Red Bull Stratos Jump. Here is a screen shot to show that I am not making this up (or that I have awesome photoshop skillz). Looking back, maybe I looked like an idiot. Really though, it wasn't my fault. I thought we were going to talk about physics. The first two questions threw me for a loop. Here are the two questions and my response (roughly paraphrased): Will Felix survive the jump? Answer: I guess so. Is there a scientific reason for this jump? Answer: I thought we were going to talk…

Faster than terminal velocity

I had so much fun creating graphs for the Red Bull Stratos Space Jump calculation, that I figured I should make some more. Can you fall faster than terminal velocity? That is the question. Air Resistance Air resistance is a force exerted on an object as it moves through some stuff - air in this case. The magnitude is usually modeled as: Rho is the density of the stuff the object is moving through A is the cross sectional area of the object C is the drag coefficient of the object - this depends on the shape (a cone would be different than a flat disk) v is the magnitude of the velocity of…

Lab: The Charge of an Electron

Not really. Here are the details (and some data) for the Millikan Oil Drop Experiment without the oil drop that I talked about previously (originally from The Physics Teacher - lucky you, it was a featured article so it should still be available (pdf)). The basic idea that Lowell McCann and Earl Blodgett from U of Wisconsin propose is to do an experiment similar to the oil drop experiment, but not so squinty (if you have done the oil drop experiment, you know what I mean). Instead of dropping charged oil in an electric field, they drop containers with metal nuts in water. The goal is to…