Coefficient of Kinetic Friction

In summary, a hockey puck is initially moving at a speed of 12 m/s on a frozen lake and after 5.0 seconds, its speed decreases to 6.0 m/s. To find the average acceleration, the mass of the object is not needed. However, to calculate the coefficient of kinetic friction between the puck and the ice, we can use the equation F=mgµ and the fact that the force on the puck is mgµ and its acceleration is F/m. By solving the equations algebraically, we can see that the mass cancels out and we can find a solution that is independent of the mass. The forces acting on the puck are gravity and the coefficient of kinetic friction between the puck and the ice.
  • #1
MakGriffith143
2
0
"A hockey puck is hit on a frozen lake and starts moving with a speed of 12 m/s. Exactly 5.0 s later, its speed is 6.0 m/s. What's the puck's average acceleration? What is the coefficient of kinetic friction between the puck and the ice?"

I've calculated the acceleration, but I'm stuck when it comes to finding the coefficient of kinetic friction since I don't know the mass of the object.
 
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  • #2
You don't need the mass of the object, just like when calculating how fast something accelerates towards the Earth you don't need to know its mass. :)
 
  • #3
How would you calculate that without the mass, though?
 
  • #4
Well, think about it. The force on the puck is mgµ, and its acceleration is F/m. Right?
 
  • #5
Solve the equations algebraically and you will see that at some point the mass cancels out of the equation providing a solution independent of the mass.
 
  • #6
Write Newton's second law for the puck. What forces acts on the puck?
 

1. What is the coefficient of kinetic friction?

The coefficient of kinetic friction is a constant value that represents the amount of resistance between two surfaces when they are in motion relative to each other. It is a dimensionless value and typically denoted by the symbol μ.

2. How is the coefficient of kinetic friction calculated?

The coefficient of kinetic friction is calculated by dividing the force of kinetic friction by the normal force acting between the two surfaces. Mathematically, it can be represented as μ = Fk/FN, where Fk is the force of kinetic friction and FN is the normal force.

3. What factors affect the coefficient of kinetic friction?

The coefficient of kinetic friction is affected by several factors, such as the roughness of the surfaces, the materials of the surfaces, the velocity of the objects, and the presence of any lubricants.

4. How does the coefficient of kinetic friction differ from the coefficient of static friction?

The coefficient of kinetic friction represents the amount of resistance between two surfaces when they are in motion, while the coefficient of static friction represents the amount of resistance between two surfaces when they are at rest. The coefficient of kinetic friction is usually lower than the coefficient of static friction.

5. Why is the coefficient of kinetic friction important?

The coefficient of kinetic friction is important for understanding and predicting the behavior of objects in motion. It helps in determining the amount of force required to keep an object in motion, as well as the distance it will travel before coming to a stop. It is also crucial in engineering applications, such as designing vehicles and machinery, to ensure proper functioning and safety.

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