Solving Physics Problem: Find Coefficient of Friction

In summary, a block of mass 25 kg rests on a horizontal surface and the coefficient of static friction is .22. If an external force of 25N acts horizontally on the block, the block will move horizontally at a constant velocity. The coefficient of static friction tells you the maximum possible force of friction acting on a stationary object.
  • #1
Eiano
12
0
Hello all,
I'm new to this site and think it's a great idea to have a Physics site to help with, b/c we all know physics is the devil... (j/k) :)

Anyway I have this problem which I think i figured out but want to be sure.



Suppose a block of mass 25 kg rests on a horizontal surface and the coefficient of static friction is .22

a). What is the maximum possible Fs that could act on the block.

This is what I got, Fs=m*g*Us
x=(25)(10)(.22) = 55N

b). What is the avtual Fs that acts on the block if an external force of 25N acts horizontally on the block.

ME:
55-25= 30M


And this problem:

2). A 5kg block rests on a horizontal plane a force of 10N applied horizontally causes the block to more horizontally at a constant velocity. What is the coefficient of friction b/w the block and the plane, assume G is 9.8 m/s^2.

My answer doesn't make sense because the coefficient is not between 0 and 1.0 :uhh:

Anyway:

ME:
(9.8)(5)/10= about 5

Any ideas?

Thanks in advance!
 
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  • #2
For 1b) the block is not moving. What must be true of the sum of the forces acting on the block?

#2 is upside down.
 
Last edited:
  • #3
Okay, so for 1b.)

since it's at equilibrium, the sum of the forces must be equal. (err, must equal 0)?

Fs= (uS)(N)?
Fs= (.22)(25)
Fs=5.5?

Is this good or am I still missing something.

and thanks for correcting my error on 2. :blushing:
 
Last edited:
  • #4
Eiano said:
Okay, so for 1b.)

since it's at equilibrium, the sum of the forces must be equal. (err, must equal 0)?

Fs= (uS)(N)?
Fs= (.22)(25)
Fs=5.5?

Is this good or am I still missing something.

and thanks for correcting my error on 2. :blushing:

The coefficient of static friction tells you the maximum possible force of friction acting on a stationary object. The actual frictional force can be any value between zero and the maximum. It is often less than the maximum, and that is true in this case.
 
  • #5
OlderDan said:
The coefficient of static friction tells you the maximum possible force of friction acting on a stationary object. The actual frictional force can be any value between zero and the maximum. It is often less than the maximum, and that is true in this case.

thanks, i read the book and didn't get this concept, thanks again for clearing it up.
 

1. What is the coefficient of friction?

The coefficient of friction is a dimensionless quantity that represents the amount of resistance between two surfaces in contact. It is a measure of the force required to move one surface relative to the other.

2. How is the coefficient of friction calculated?

The coefficient of friction can be calculated by dividing the force of friction by the normal force between the two surfaces. It can also be determined experimentally by measuring the force required to move an object and dividing it by the weight of the object.

3. Why is finding the coefficient of friction important?

The coefficient of friction is important because it helps us understand the amount of resistance between two surfaces and how that affects motion. It is also useful in predicting and analyzing the behavior of objects in different situations, such as on an inclined plane or in a pulley system.

4. What factors affect the coefficient of friction?

The coefficient of friction can be affected by several factors, including the roughness of the surfaces in contact, the type of materials involved, and the presence of lubricants or other substances between the surfaces.

5. What are some real-life examples of using the coefficient of friction?

The coefficient of friction is used in many everyday situations, such as driving a car (the tires gripping the road), walking (shoes on the ground), and playing sports (a soccer ball on a field). It is also important in engineering and design, such as when determining the stability of structures or the performance of machinery.

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