# Kinetic friction, i forgot

1. Nov 25, 2004

### nemzy

here is the problem:

a 0.215 kg metal rod carrying a current of 11.8 A glides on two horizontal rails 0.460 m apart. What vertical magnetic field is required to keep the rod moving at a constant speed if the coefficient of kinetic frictin between the rod and rails is .120?

i forgot what kinetic friction is, and what the formula is..If i knew that i could easily solve tihs problem. I only have volume 2 of my physics book which doesnt go over this, and i learned this over a year ago and i forgot what it is..Can someone please refresh my memory? thanks

2. Nov 25, 2004

### Chen

Kinetic friction is given by:
$$f_k = N\mu_k$$
Where N is the normal force and uK is the coefficient of kinetic friction.

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