How to find the coefficient of Friction?

In summary, A small 15 kg cardboard box is thrown across a level floor, sliding a distance of 7.0 m and stopping in 3.3 s. The forces on the box's free-body diagram include gravity, normal force, and friction. Deceleration is not given, but can be found using the equation ƩF=ma. The average speed and initial speed can also be calculated. With the given data, the deceleration can be found using kinematics. Once deceleration is determined, the friction coefficient can be computed by equating the initial kinetic energy with the energy loss due to friction.
  • #1
luxford
2
0

Homework Statement



A small 15 kg cardboard box is thrown across a level floor. It slides a distance of 7.0 m, stopping in 3.3 s. What is the coefficient of friction between the box and the floor?

Homework Equations





The Attempt at a Solution



I didn't know how to do it. I just drew a free-body diagram of it. :|
 
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  • #2
What forces do you have in your FBD? What is the deceleration (a) according to your forces equation and (b) according to the given data?
 
  • #3
The forces I have on my FBD is the force of gravity, normal force, and force of friction.

As for deceleration, it is not given...
 
  • #4
luxford said:
The forces I have on my FBD is the force of gravity, normal force, and force of friction.

As for deceleration, it is not given...
You know the equation ƩF=ma, right? Apply this in the horizontal and vertical directions to obtain two equations.
 
  • #5
luxford said:

Homework Statement



A small 15 kg cardboard box is thrown across a level floor. It slides a distance of 7.0 m, stopping in 3.3 s. What is the coefficient of friction between the box and the floor?

Homework Equations





The Attempt at a Solution



I didn't know how to do it. I just drew a free-body diagram of it. :|

What's the average speed? So then what's the initial speed?
Then, can we equate initial k.e. with friction energy loss to compute the friction coefficient?
 
  • #6
luxford said:
The forces I have on my FBD is the force of gravity, normal force, and force of friction.

As for deceleration, it is not given...

If you have t, d, and vf, you can find the deceleration using kinematics.

Since you have all three of these, finding deceleration is quite simple.

d=vft+[itex]\frac{1}{2}[/itex]at2
 

1. What is the coefficient of friction?

The coefficient of friction is a measure of the resistance between two surfaces in contact. It indicates how difficult it is to slide one object over another.

2. How is the coefficient of friction measured?

The coefficient of friction is typically measured using a device called a friction tester. This instrument applies a known force to one surface and measures the force required to move the other surface.

3. What factors can affect the coefficient of friction?

The coefficient of friction can be influenced by several factors, including the roughness of the surfaces, the materials of the surfaces, the temperature, and the presence of any lubricants or contaminants.

4. How can the coefficient of friction be calculated?

The coefficient of friction can be calculated by dividing the force required to move one surface over the other by the normal force between the two surfaces. This calculation is typically done using the formula μ = F/N, where μ is the coefficient of friction, F is the force, and N is the normal force.

5. Why is the coefficient of friction important?

The coefficient of friction is important in many practical applications, such as designing machinery, selecting appropriate materials for different surfaces, and ensuring safety in various industries. It also plays a crucial role in understanding and predicting the behavior of objects in motion.

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