Mass Friction problem

  • Thread starter lockedup
  • Start date
  • #1
70
0

Homework Statement

mass 1 is 2.0 kg, the static and kinetic coefficients of friction are .30 and .20 respectively.

a) What is mass 2 if it travels uniformly upward?
b) Downward?
c) mass 1 and 2 are at rest?



Homework Equations





The Attempt at a Solution



Part c is the easiest. Friction and Tension are going to be the same so [tex]m_{2} = \mu_{s}m_{1}[/tex].

Part a, I did the same thing about except I used [tex]\mu_{k}m_{1}[/tex].

Part b, [tex]m_{1}g = \mu_{k}m_{1}g[/tex]
[tex]m_{2} = m_{1}/\mu_{k}[/tex]

Is this right?

Why is it that I can ace Abstract Algebra but this gives me a headache?
 

Answers and Replies

  • #2
tiny-tim
Science Advisor
Homework Helper
25,832
251
Hi lockedup! :smile:

erm :redface: … what is the set-up? :confused:
 
  • #3
93
0
I'm guessing its a triangular slope of some sort with one mass on either side.
 
  • #4
tiny-tim
Science Advisor
Homework Helper
25,832
251
Hi inutard! :smile:
I'm guessing its a triangular slope of some sort with one mass on either side.

ah, but then we'd have heard about a θ :wink:
 
  • #5
93
0
Good point. Maybe its in the diagram that he is neglecting to show us (As he also mentions tension but he neglected to talk about a rope or string in his question).
 
  • #6
70
0
Damn, I forgot to attach the picture! I'm a she BTW... lol
 

Attachments

  • problem.jpg
    problem.jpg
    7.5 KB · Views: 284
  • #7
tiny-tim
Science Advisor
Homework Helper
25,832
251
(just got up :zzz: …)

Hi lockedup (f.)! :wink:

mmm … inutard :smile: guessed right! :biggrin:

ok then, there's a θ = 37º, which isn't in your equations …

put it in now …

what do you get? :smile:
 
  • #8
93
0
Pardon me about the gender mixup! Remember that theres not only frictional force opposing direction of motion but also a force to the bottom-left (depending on the angle) that is caused by the normal force on block m1
 

Related Threads on Mass Friction problem

  • Last Post
Replies
1
Views
3K
  • Last Post
Replies
1
Views
2K
Replies
2
Views
6K
  • Last Post
Replies
3
Views
2K
  • Last Post
Replies
2
Views
525
Replies
11
Views
741
Replies
9
Views
3K
  • Last Post
Replies
3
Views
519
Replies
3
Views
2K
  • Last Post
Replies
3
Views
935
Top