Centripetal Force/Changing direction on ice - Turn length

Click For Summary

Homework Help Overview

The problem involves calculating the smallest turn a person can make while running on ice, given their speed, mass, and the coefficient of friction. The subject area includes concepts of centripetal force and friction in a dynamics context.

Discussion Character

  • Exploratory, Conceptual clarification, Mathematical reasoning

Approaches and Questions Raised

  • The original poster attempts to calculate the radius of the turn using the net force equations and friction. Some participants clarify that the question may involve finding the length of the arc for a quarter turn, leading to discussions about the relationship between radius and circumference.

Discussion Status

Participants are exploring the relationship between the radius of the turn and the arc length. There is a recognition of the calculations made regarding the radius, and some guidance is offered on interpreting the problem in terms of circular motion.

Contextual Notes

There is some confusion regarding the interpretation of the problem, particularly in understanding the motion involved and the specific question being asked about the turn length.

testme
Messages
68
Reaction score
0

Homework Statement


I am running to school at 6m/s when I hit a patch of icy sidealk. The coefficient of friction between the ice and my shoes is 0.16. I wish to turn my 55kg frame to the left. What is the smallest turn I can make?

v = 6 m/s
μ = 0.16
m = 55 kg

Homework Equations


Fnet = mv^2/r
Ff = μFn
Fnet = ma

The Attempt at a Solution


Assume that up and left are positive.

Fnet = ma
Fg + Fn = ma
-539 + Fn = 0
Fn = 539

Ff = μFn
Ff = 0.16 (539)
Ff = 86.24

Fnet = mv^2/r
Ff = mv^2/r
86.24 = 55(6)^2/r
86.24 = 1980/r
r = 23 m

I'm not sure if that's the answer or what to do next, or even if what I did is the right method. The question is kind of confusing me because I don't fully understand how the person is moving.
 
Physics news on Phys.org
testme said:
r = 23 m

I'm not sure if that's the answer or what to do next, or even if what I did is the right method. The question is kind of confusing me because I don't fully understand how the person is moving.

You got the radius of the circle (correct) the boy can turn without slipping outwards. He wants to turn to the left, change direction by 90 degrees. Instead of just turning round his body, he makes the turn along an arc. I think the problem asks the length of the arc.

ehild
 

Attachments

  • turn.JPG
    turn.JPG
    2.8 KB · Views: 458
So you mean like a quarter of the circumference?

C = 2∏r
C = 46∏
C = 145
C/4 = 36.25m

Therefore the smallest turn the boy can make is 36.25m?
 
testme said:
So you mean like a quarter of the circumference?

C = 2∏r
C = 46∏
C = 145
C/4 = 36.25m

Therefore the smallest turn the boy can make is 36.25m?

That is, (pi/2)*R. . Yes, I think, that was the question.

ehild
 

Similar threads

  • · Replies 8 ·
Replies
8
Views
2K
  • · Replies 5 ·
Replies
5
Views
2K
  • · Replies 7 ·
Replies
7
Views
2K
  • · Replies 4 ·
Replies
4
Views
4K
  • · Replies 1 ·
Replies
1
Views
2K
  • · Replies 15 ·
Replies
15
Views
5K
  • · Replies 13 ·
Replies
13
Views
2K
  • · Replies 1 ·
Replies
1
Views
1K
  • · Replies 1 ·
Replies
1
Views
2K
Replies
2
Views
4K