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Static friction

  • Thread starter vitesse86
  • Start date
  • #1
8
0

Homework Statement



I have a general question about circular motion of a car on a flat curve.
What must the static friction koefficient be if the car can make the swing by 60km/h?

Thank you,

Homework Equations



- We have to follow newtons 2nd law.

- Fcentripetal = m*(v^2/r)

known stats:
r= 150m
v= 16,67m/s
g= 9,81



The Attempt at a Solution



mg = v2/r /g

m= v2/r*g

m= ((16,67*16,67)/(150*9,81))

m= 0.189


Need probably help here, not sure if I did do the equations right.
 
Last edited:

Answers and Replies

  • #2
145
0
Surely they must also have given you the radius of the track?

Have you any idea how to start the problem?
 
  • #3
8
0
Surely they must also have given you the radius of the track?

Have you any idea how to start the problem?
Hi,

the radius is 150m.

Thanks,
 
  • #4
8
0
Can someone help me please, need help as soon as possible.



, thanks!
 
  • #5

Homework Statement



I have a general question about circular motion of a car on a flat curve.
What must the static friction koefficient be if the car can make the swing by 60km/h?

Thank you,

Homework Equations





The Attempt at a Solution


So, frictional force equals to centripetal force, and also equals to that coefficient times normal force.

Find centripetal, and thus that's the frictional force (it's keeping the car in that circle)
and then
Fn.coefficient = Centripetal force
mass cancels out..
and
so
g.coefficient = centripetal acc..

hoping this would help
 
Last edited:
  • #6
8
0
So, frictional force equals to centripetal force, and also equals to that coefficient times normal force.

Find centripetal, and thus that's the frictional force (it's keeping the car in that circle)
and then
Fn.coefficient = Centripetal force
mass cancels out..
and
so
g.coefficient = centripetal acc..

hoping this would help

Hi,
thanks for the help.
But can't you help me a little closer, I am pretty new to this and I am also a newbee.

Thanks,
 
  • #7
Centripetal = v^2/r
v=60 km/hr -- convert this is m/s
r=150 m

g.Answer = (v^2/r)
Answer = (v^2/r).g

sounds like a weird answer.. perhaps me wrong
 
  • #8
8
0
Centripetal = v^2/r
v=60 km/hr -- convert this is m/s
r=150 m

g.Answer = (v^2/r)
Answer = (v^2/r).g

sounds like a weird answer.. perhaps me wrong
Can somebody help us here, please honestly!!
 
  • #9
312
0
g.Answer = (v^2/r)
Thats it, just make sure you convert units and then divide by g
 
  • #10
8
0
Thats it, just make sure you convert units and then divide by g
My english are abit bad, can you please write down for me how to do this?

f_on_car_1.gif

use this as a helping figure.
 
Last edited:
  • #11
hmm.. ite

so,
the answer for your question is = (v^2/(r.g))
v=16.67 m/s
r=150 m
g= 9.81

and so answer = 0.189
 
  • #12
8
0
hmm.. ite

so,
the answer for your question is =
v=16.67 m/s
r=150 m
g= 9.81

and so answer = 0.189
Can you show me the calculations how u did come
to (v^2/(r.g)) ?

Sorry I am a very newbee, and need everything in with a big fork:grumpy:



please help someone.:frown:
 
  • #13
cristo
Staff Emeritus
Science Advisor
8,107
73
Can you show me the calculations how u did come
to (v^2/(r.g)) ?
Since this is a homework question, noone will calculate the answer for you. In fact, harmeet has given you lots of help, considering the fact that you have done nothing yet.

How about filling in numbers 2 and 3 in the homework posting template. What do you know? e.g. Do you know the equation to calculate centripetal force?
 
  • #14
8
0
Since this is a homework question, noone will calculate the answer for you. In fact, harmeet has given you lots of help, considering the fact that you have done nothing yet.

How about filling in numbers 2 and 3 in the homework posting template. What do you know? e.g. Do you know the equation to calculate centripetal force?
You are right.

There, i did filling in, and did an attempt.

Was it right or?


thanks for any help,
 

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