• Support PF! Buy your school textbooks, materials and every day products Here!

Minimal coefficient of friction

  • Thread starter Karol
  • Start date
  • #1
1,380
22

Homework Statement


The rectangle in the drawing is held by the horizontal rope and the friction on the wall.
What's the minimal coefficient of friction

Homework Equations


Friction force: f=μN

The Attempt at a Solution


Moments round the point of contact with the wall. the side of the rectangle is a, half the diagonal to the center is ##\sqrt {a}##. the distance of the CoM to the wall: ##\sqrt {a}\cdot\sin 55^0=1.16a##
$$1.16a\cdot mg=T\cdot \sin 10^0\rightarrow T=6.68mg$$
$$6.68mg\cdot\mu=mg\rightarrow\mu=0.15$$
It should be 0.3
 

Attachments

Answers and Replies

  • #2
BvU
Science Advisor
Homework Helper
2019 Award
13,050
3,024
So from the wall to the center of mass is 1.16 times the length of a side ? That's in mid-air ! ;)
 
  • #3
CWatters
Science Advisor
Homework Helper
Gold Member
10,529
2,295
Is it a square or rectangle? If it's a square check your calculation for "half the diagonal".
 
  • #4
1,380
22
So from the wall to the center of mass is 1.16 times the length of a side ? That's in mid-air !
I thank you very much BvU for i didn't laugh so much for some time
 
  • #5
130
30
I believe what you used for the normal force is incorrect.
 
  • #6
BvU
Science Advisor
Homework Helper
2019 Award
13,050
3,024
  • #7
1,380
22
The distance of CoM from the wall: ##\frac{a}{\sqrt{2}}\cdot\sin 55^0=0.58a##
$$0.58a\cdot mg=T\cdot \sin 10^0\rightarrow T=3.41mg$$
$$3.41mg\cdot\mu=mg\rightarrow\mu=0.3$$
 

Related Threads on Minimal coefficient of friction

  • Last Post
Replies
1
Views
7K
Replies
1
Views
284
Replies
3
Views
832
Replies
0
Views
916
Replies
10
Views
6K
Replies
7
Views
4K
Replies
1
Views
51K
  • Last Post
Replies
8
Views
697
  • Last Post
Replies
5
Views
2K
Top