what is the average friction force when a person has a usual 1 km walk ?
Welcome to PF, Sunny.
Your question, as asked, is impossible to answer. Much more information is needed. For one thing, you have to consider the level of synovial fluid in the body joints to determine the friction involved just within the body itself, before you even get to what kind of shoes (if any) the subject is wearing on what kind of surface, under what conditions.
I suppose you could come up with a wild estimate of the answer by estimating the force applied by the walker's feet in order to maintain a constant velocity. If there were no friction, then once he got going he'd just coast along at a constant speed (like an ice skater), so whatever force he's applying could be thought of as the force needed to overcome friction.
Of course, the real story is much more complicated than that, but it's a start, at least.
If there was no friction, he couldn't get going in the first place. :tongue:
Not unless he had something to throw!
Well, I always keep a halibut around for just that purpose...
edit: Lest anyone thinks that I'm racist, a salmon would work just as well.
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