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# Physics/Information On Friction

Question
QUESTION: Hi. I am from the Island City Academy. I am doing a project on slinkys. I would like to see if you would be willing to be my expert. I would like to know how much worse and friction would be on the slinky when it would be going down stairs. I you could get back to me that would be great.

Danielle

ANSWER: Perhaps you can clarify what you mean by "worse and friction."  I'm not sure what that means.

---------- FOLLOW-UP ----------

QUESTION: I ment to say How much friction was on the slinky before and after it goes down the stairs. Sorry my audio correction.

Well, a slinky just sits there before it goes down the stairs.  Same after.  Friction really isn't as big of a part of a slinky's motion as you might think, aside from the static friction that holds the ends in place as the main coil moves.  The spring force plays a much larger role in each step, and that force derives from shear stress on the metal in the coils.  Shear strain (how much the metal in each coil bends as the slinky takes a step) is what allows the slinky to move from the upper step.  The slinky acquires momentum as it takes the step, which carries over into the next step.  The response force from the bending metal keeps the slinky from moving too quickly.  It would be difficult to do any measurements on such a system, since the slinky moves relatively quickly.  What is the goal of your project?

Physics

Volunteer

#### Dr. Stephen O. Nelson

##### Expertise

I can answer most basic physics questions, physics questions about science fiction and everyday observations of physics, etc. I'm also usually good for science fair advice (I'm the regional science fair director). I do not answer homework problems. I will occasionally point out where a homework solution went wrong, though. I'm usually good at explaining odd observations that seem counterintuitive, energy science, nuclear physics, nuclear astrophysics, and alternative theories of physics are my specialties.

##### Experience

I was a physics professor at the University of Texas of the Permian Basin, research in nuclear technology and nuclear astrophysics. My travelling science show saw over 20,000 students of all ages. I taught physics, nuclear chemistry, radiation safety, vacuum technology, and answer tons of questions as I tour schools encouraging students to consider careers in science. I moved on to a non-academic job with more research just recently.

Education/Credentials
Ph. D. from Duke University in physics, research in nuclear astrophysics reactions, gamma-ray astronomy technology, and advanced nuclear reactors.