Does the coefficient of kinetic friction depend on speed?
2006-10-18 06:37:04 · 6 answers · asked by Anonymous in Science & Mathematics ➔ Physics
I meant, like 2 pieces of wood. 1 moving on top of the other
2006-10-18 06:45:05 · update #1
No it doesn't. It depends only on the materials that are in contact.
2006-10-18 07:27:25 · answer #1 · answered by Dimos F 4 · 1⤊ 0⤋
No, the coefficient (k) in Ff = kN depends solely on the materials of the moving body and the surface it is moving on. While in special cases (like fluids) there are some relationships used to calculate k, in the overwhelming majority of cases k is empirically derived from countless experiments.
Ff is the frictional force acting along the surface in a direction opposite to the motion of the sliding body. N is the normal weight of the body, where N = W cos(deg) and W = mg, the weight of the body, and deg is the angle between the horizontal and the ramp the body might be on. For example, if the surface is horizontal, cos(deg = 0) = 1; so that N = W = mg.
The person who used air friction to claim the coefficient depended on speed was in error. Friction causes drag forces as bodies move through air. Drag forces are found by Fd = 1/2 Cd A rho v^2; where A is the cross sectional area across the direction of the body, rho is air density, v is the velocity of the body re the air, and, ta da, Cd is the drag coefficient, which depends solely of characteristics of the body (shape, material, etc.), not speed or velocity. Cd is the coefficient of friction for drag forces.
2006-10-18 07:25:26 · answer #2 · answered by oldprof 7 · 1⤊ 0⤋
Never heard it called that. Static friction is for the case of something not moving. Then sliding friction.
Sliding friction is general used with no adjustment for speed.
Speed is considered by a term called PV pressure and velocity for various bearing materials.
2006-10-18 06:46:00 · answer #3 · answered by Roadkill 6 · 0⤊ 0⤋
depending on material. Like the human body is warm through natrual friction through the miles of veins and constant pumping of the heart.
Water itself has this going. Ever stepped in water in hard rain? An entire river can suddenly be a good deal warmer in hard rain, not enough to be boiling or even mildly hot. Forced and natural friction are the same. Stationary or living, it's all friction.
2006-10-18 06:43:32 · answer #4 · answered by Anonymous · 0⤊ 1⤋
Yes. Air friction increases with speed, and that is part of kinetic friction. If kinetic friction didn't increase with speed, there wouldn't be such a thing as terminal velocity.
2006-10-18 06:48:35 · answer #5 · answered by nospamcwt 5 · 0⤊ 2⤋
Other than air or water resistance, I would say no.
2006-10-18 07:20:44 · answer #6 · answered by Randy G 7 · 0⤊ 0⤋