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Friction and Normal Force

  • Thread starter phizics09
  • Start date
  • #1
35
1

Homework Statement



A pizza box thrown across the room strikes
the floor with a horizontal velocity of 2.0 m/s.

Homework Equations



If the 300-g box encounters a floor with a
coefficient of kinetic friction of 0.3, how far
will the box slide before coming to rest?


The Attempt at a Solution


So I did it by using the equation a=ug(u is coefficient of kinetic friction), and I got -2.94 m/s^2 as the acceleration. Then, I used a kinematics equation and found d to be 0.68 m, but the answer says its 0.068 m. Is the answer at the back wrong?

Also, I was wondering if the given 300g mass of the box was needed in the solution?
 

Answers and Replies

  • #2
PeterO
Homework Helper
2,425
46

Homework Statement



A pizza box thrown across the room strikes
the floor with a horizontal velocity of 2.0 m/s.

Homework Equations



If the 300-g box encounters a floor with a
coefficient of kinetic friction of 0.3, how far
will the box slide before coming to rest?


The Attempt at a Solution


So I did it by using the equation a=ug(u is coefficient of kinetic friction), and I got -2.94 m/s^2 as the acceleration. Then, I used a kinematics equation and found d to be 0.68 m, but the answer says its 0.068 m. Is the answer at the back wrong?

Also, I was wondering if the given 300g mass of the box was needed in the solution?
I like your answer, and you don't need the mass - unless you are unaware of the a = μg arrangement and want to do it from first principles..
 
  • #3
35
1
So my answer is right?
 
  • #4
PeterO
Homework Helper
2,425
46
So my answer is right?
I think so. It would take 3g acceleration to slow from 2 m/s in only 0.068 m.
 

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