Find friction coefficient given initial and final velocity

In summary, the problem involves finding the coefficient of friction of a mythical frictionless surface given initial and final velocities and distance traveled. To solve this problem, one must use the equations for motion under constant acceleration and draw a free-body diagram to identify and list all the forces acting on the box. The general procedure for solving this type of problem is to identify known and unknown variables, and use the appropriate equations and diagrams to find the desired variable.
  • #1
tyger2020
I am not sure how to approach a problem involving the friction coefficient when only given initial velocity, final velocity, and distance traveled. I could combine the friction and kinematic equations, but I am only familiar with doing that for one velocity...

Here is the specific problem I had trouble with:

A cardboard box of unknown mass is sliding upon a mythical frictionless surface.

The box has a velocity of 4.56 m/s when it encounters a bit of friction. After sliding 0.700m, the box has a velocity of 3.33 m/s.

What is the coefficient of friction of the surface?

How do I solve this problem in particular, and what is the general procedure to solve problems like this?
 
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  • #2
Welcome to PhysicsForums.
If you have not already, please take a moment to read over the rules, especially the part about how the Homework Help works.
You can find that here - https://www.physicsforums.com/threads/physics-forums-global-guidelines.414380/

When you use the homework template, it allows us to clearly see the problem statement, and what you know, and what you have tried.

Look at what information you have, and what you are able to calculate from the information (acceleration, perhaps?) Could that be of assistance here? What information do you need, in order to calculate friction?
 
  • #3
tyger2020 said:
How do I solve this problem in particular, and what is the general procedure to solve problems like this?
What equations for motion under constant acceleration have you been taught?
 
  • #4
tyger2020 said:
what is the general procedure to solve problems like this?

In addition to those equations for motion, you also want to draw a free-body diagram detailing all the forces acting on the box, in addition to identifying and listing your variables. What are your known variables? Which variables do you not know? Which variable must you find?
 
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1. What is the formula for finding the friction coefficient given initial and final velocity?

The formula for finding the friction coefficient, µ, is µ = (vf - vi) / (g * t), where vf is the final velocity, vi is the initial velocity, g is the acceleration due to gravity, and t is the time taken for the change in velocity.

2. What are the units for the variables in the friction coefficient formula?

The final and initial velocities should have the same units, such as meters per second (m/s). The acceleration due to gravity is typically measured in meters per second squared (m/s2). The time taken should be in seconds (s). Therefore, the units for the friction coefficient will be in m/s2.

3. Can the friction coefficient be negative?

Yes, the friction coefficient can be negative. A negative value indicates that the friction force is acting in the direction opposite to the motion, resulting in a decrease in velocity.

4. How does the mass of an object affect the friction coefficient?

The mass of an object does not directly affect the friction coefficient. However, a heavier object may experience a greater frictional force due to its weight, resulting in a larger change in velocity and a potentially higher friction coefficient.

5. Is the friction coefficient constant for all surfaces and conditions?

No, the friction coefficient can vary depending on the surfaces in contact and the conditions, such as the presence of lubricants or the roughness of the surfaces. It is important to consider these factors when calculating the friction coefficient.

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