Friction problem

[Oslo]

Hello!

I have just started physics here in Norway, and we have a home assignement due to friday. I sat all yesterday trying to figuer out what friction coefficient to use in my assignment. Here is the assignment:

Two objects are lying on an horizontal table, tied together with a very light rope, object 1 has the mass of 2Kg and object 2 has the mass of 4Kg.

Object one has friction coefficient = 0.1
Object two har friction coefficient = 0,15

The Force applied on the rope tied to object 2 has a force of 60N...

Object 1----------object 2----------------> F=6N

Do i calculate with 0.25 as a friction coef.? or both individually intergrated into F-(Mju*g+(m1+m2)/(m1+m2) . To find the acceleration

Please give me some hints.

Hopefully you understand my english :)

thanks
Cns/Oslo

 

[andrevdh]

Consider each object separately. Apply Newton's second law (the sum of all of the forces that an object experiences is equal to it's mass times it's acceleration) for each object separately in the direction of F. Each object has it's own frictional force (which can be calculated). Both objects share the same acceleration though. You will end up with two equations with the same tension in both. Add the two equations up and solve for the acceleration.

 

[Oslo]

Thank you so much, you have been to great help!

 

[andrevdh]

Glad I could help you.