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

Coefficient of Kinetic Friction

  • #1
"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.
 

Answers and Replies

  • #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
1,948
200
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
3,741
418
Write Newton's second law for the puck. What forces acts on the puck?
 

Related Threads on Coefficient of Kinetic Friction

  • Last Post
Replies
2
Views
951
  • Last Post
Replies
1
Views
1K
  • Last Post
Replies
4
Views
1K
  • Last Post
Replies
4
Views
13K
  • Last Post
Replies
6
Views
896
  • Last Post
Replies
1
Views
2K
  • Last Post
Replies
4
Views
8K
  • Last Post
Replies
2
Views
878
  • Last Post
Replies
21
Views
955
  • Last Post
Replies
1
Views
2K
Top