Paintball Guns and Gear forums banner

1 - 19 of 19 Posts

·
Imperator
Joined
·
19,071 Posts
Discussion Starter #1
"Unbeknownst to the students, every time the school floors are waxed, Mr. Tracy, the principal, likes to slide down the hallway in his socks. Mr. Tracy weighs 850N and the coefficient of sliding friction between his socks and the floor is 0.120. What is the force of friction that opposes Mr. Tracy's motion down the hall?"

I forget how to figure that out, anyone know?
 

·
Registered
Joined
·
1,903 Posts
im not sure, since i dont have physics til next semester, but by the looks of it, it is a fairly easy problem. most likely you have to multiply or divide the two numbers, and probably need another number that you have wrote down or something. than maybe cross multiply it. but idk im probably wrong
 

·
Imperator
Joined
·
19,071 Posts
Discussion Starter #5
Soljah said:
oh god.. im going to go look this up for you then edit this if Nobody replies.. but if I may ask, what grade/class is this in?

No class, just trying to improve myself by doing a little outside studies. (Yes, I know the concept of study is unbeknownst to most in the American school system.) ;)
 

·
Cunning Linguist
Joined
·
2,273 Posts
Soljah said:
yep yep, just found it in my texbook,

Force of Friction = Coefficient of Friction Times The Normal Friction
It's not the normal friction, its the normal force: the force applied by gravity.
 

·
Imperator
Joined
·
19,071 Posts
Discussion Starter #12
I think it is a trick question though, because it relys on the fact that the floor is perfectly uniform....which I doubt. ;)
 

·
Cunning Linguist
Joined
·
2,273 Posts
Nothing in theoretical physics makes sense in actuality. You have to assume the floor is uniform or the problem can't be done without more complicated algorithms. His socks probably aren't uniform either. Technically Mr. Tracy is losing mass as dead skin falls from his body at a rate of something along the lines of 1mg/hour. It's not only the force of friction that resists Mr. Tracy, there is also wind resistance. How can we know that the floor is perfectly level, perhaps it is an incline of 0.001 degrees. This is why we don't question the assumptions we make when we do physics problems.
 

·
Imperator
Joined
·
19,071 Posts
Discussion Starter #14
That is what bothers me about physics, it isn't concrete enough for my taste, but then again most everything is relative.
 

·
Cunning Linguist
Joined
·
2,273 Posts
You have to understand it under ideal conditions before you can begin to understand it under adverse conditions. You gotta walk before you can run.
 
D

·
Guest
Joined
·
0 Posts
Angered Fists said:
Fn x u = Fr

Normal force times mu equal force of resistance so 850 x .120 = 102N
correct.. so you guys are forced to work in metric system in physics?

btw.. it say he weighs 850 newtons correct? which confuses me.. cuz mass is given in the SI base unit Kg (kilograms) not newtons.. maybe the question messed it? or you did paul? maybe they mean thats the force he exerts on the ground?

but... normal force is equal to the force of gravity.. we calculate teh force of gravity on an object by mass * 9.81 kg/s .. so that gives you normal force.. then you multiply that by mu (coefficient of friction)
 
1 - 19 of 19 Posts
Top