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Kinematic/Dynamic question

  • Thread starter ExtendedG
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Homework Statement


A sled takes off from the top of a hill inclined at 6 degrees to the horizontal. The sled's initial speed is 12 m/s. The coefficient of friction between the sled and the snow is 0.14. Determine how far the sled will slide before coming to rest.


Homework Equations


F=ma
vFsquared=vIsquared + 2a(d)
vf= velocity final vI= initial velocity a=accel. d=displacement.


The Attempt at a Solution


Well I didn't get very far because I don't have enough variables, I need mass! I obviously need to find accelerating, what would my f=ma statement be? I thought it would be Fapp - Ffriction = ma........help?
 

Answers and Replies

  • #2
CWatters
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Perhaps worth remembering the definition of coefficient of friction. It's the ratio of two forces one of which depends on the mass. This means that mass sometimes cancels in some problems so it's not allways needed.

Draw the free body diagram and write equations for the forces.
 
  • #3
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Perhaps worth remembering the definition of coefficient of friction. It's the ratio of two forces one of which depends on the mass. This means that mass sometimes cancels in some problems so it's not allways needed.

Draw the free body diagram and write equations for the forces.
F=ma
Fg - Ff = ma
mgsin(theta) - umgcos(theta) = ma
I have two masses to remove, not just one :/ So i can't just simply simplify to:
gsin(theta) - ugcos(theta) = a right?
 

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