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

Rotational Kinematics- sphere

  • Thread starter mattmannmf
  • Start date
  • #1
172
0
A solid sphere of uniform density starts from rest and rolls without slipping a distance of d = 4.2 m down a q = 26° incline. The sphere has a mass M = 5.1 kg and a radius R = 0.28 m.

a) Of the total kinetic energy of the sphere, what fraction is translational?


b) Suppose now that there is no frictional force between the sphere and the incline. Now, what is the translational kinetic energy of the sphere at the bottom of the incline?

I figured out that KEtran is 65.8 j. I figured out that the phere reaches the bottom of the ramp at a speed of 5.08. the magnitude of friction forceon the sphere is 6.25 N. I just dont know what to do for a or b...any help?
 

Answers and Replies

  • #2
Doc Al
Mentor
44,874
1,122
I just dont know what to do for a or b...any help?
If there's no friction, what fraction of the total KE is translational?
 
  • #3
172
0
all?
 
  • #4
Doc Al
Mentor
44,874
1,122
all?
Right. Without the torque due to friction, it will slide down the incline without rolling.
 
  • #5
172
0
ok so that would be for b. Im still kind of stuck on a.
 
  • #6
172
0
im confused on how to find the total kinetic energy
 
  • #7
Doc Al
Mentor
44,874
1,122
im confused on how to find the total kinetic energy
Assuming that you posted the problem completely, for a you don't need to find the actual total energy, just the fraction that's translational. (Don't plug in any specific numbers.)

Express the translational and rotational KE and see how they relate for a sphere rolling without slipping. Hint: How does ω relate to translational speed?
 

Related Threads for: Rotational Kinematics- sphere

Replies
2
Views
8K
Replies
4
Views
1K
  • Last Post
Replies
3
Views
1K
  • Last Post
Replies
1
Views
3K
  • Last Post
Replies
1
Views
2K
  • Last Post
Replies
22
Views
2K
  • Last Post
Replies
2
Views
1K
  • Last Post
Replies
10
Views
2K
Top