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

Puck on Ice

  • Thread starter Psyguy22
  • Start date
  • #1
62
0
A hockey puck on a frozen pond with an initial speed of 12.3 m/s stops after sliding a distance of 198.9 m. Calculate the average value of the coefficient of kinetic friction between the puck and the ice.

So I started with finding the acceleration. I divided 12.3m/s by 198.9m then took the inverse (so units would go back seconds) and came up with 16.17s. So now I have Δv and Δt so I divided 12.3m/s by 16.17s to get an acceleration of .76m/s^2

I also know that friction equals μN and that F=ma. Since N=mg and friction is the only force acting on the object, i divided the mass out. So I had μg=a, or μ=a/g. (using 9.81m/s^2 as gravity) So μ=.0774 which seemed reasonable for ice. But I dont know how to find the actual force without knowing the mass. Am I even heading in the right direction?
 

Answers and Replies

  • #2
34,043
9,891
So I started with finding the acceleration. I divided 12.3m/s by 198.9m then took the inverse (so units would go back seconds) and came up with 16.17s. So now I have Δv and Δt so I divided 12.3m/s by 16.17s to get an acceleration of .76m/s^2
That does not work.
To travel 198.9m in 16.17s, it would have to travel at 12.3m/s the whole time, which is clearly not the case. You need a different approach here.

I also know that friction equals μN and that F=ma. Since N=mg and friction is the only force acting on the object, i divided the mass out. So I had μg=a, or μ=a/g. (using 9.81m/s^2 as gravity) So μ=.0774 which seemed reasonable for ice. But I dont know how to find the actual force without knowing the mass. Am I even heading in the right direction?
That part is good, once you fix your acceleration value. You cannot, and do not have to, calculate the force.
 
  • #3
62
0
Then how do I find acceleration? I don't have time..
 
  • #4
137
4
But you do know lots of other things. For example, you know the initial and the final speeds. I think it's okay to assume uniform acceleration here. You probably have a list of equations for dealing with this sort of motion that look something like, for example, v = u + at.

What you need to do is find an equation that includes the quantities that you know along with the acceleration. Then there's some algebra to find a.
 

Related Threads on Puck on Ice

  • Last Post
Replies
1
Views
2K
  • Last Post
Replies
6
Views
453
Replies
4
Views
3K
  • Last Post
Replies
5
Views
5K
Replies
2
Views
1K
Replies
12
Views
2K
Replies
3
Views
1K
Replies
3
Views
927
Replies
3
Views
9K
Replies
2
Views
1K
Top