Towing two stacked boxes up a ramp

[Sebee_ulg]

Homework Statement

A man pulls two boxes along a ramp of length L = 4.75 m and height H = 2.5 m. To do this, he pulls on a rope attached to the first box of mass m1 = 48 kg. The second box has a mass m2 = 32 kg and is placed on top of the first. The coefficient of friction between the first box and the floor is µ1 = 0.444 and the coefficient of friction between the two boxes is µ2 = 0.8.

Relevant Equations

(a) the force to be applied to move the two boxes at a constant speed constant v = 1.5 m/s. (b) the maximum force that can be applied to the string to ensure that the two boxes to remain stationary relative to each other. (c) What will be the speed of the boxes after travelling 1 m?

Answer is (a) F ≃ 675 (N); (b) F ≃ 859 (N) (c) v ≃ 2.2 (m/s).

 

[BvU]

!

Please read
https://www.physicsforums.com/threads/homework-help-guidelines-for-students-and-helpers.686781/

And: what is your question ?

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[Sebee_ulg]

!

Please read
https://www.physicsforums.com/threads/homework-help-guidelines-for-students-and-helpers.686781/

And: what is your question ?

$\$

Sorry, I hadn't read the instructions and my question is that I can't find the right result for question b.

 

[BvU]

Sorry, I hadn't read the instructions and my question is that I can't find the right result for question b.

Mainly: what is your best effort ?

And: what are the relevant equations you need to get going on this exercise ?

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[haruspex]

Sorry, I hadn't read the instructions and my question is that I can't find the right result for question b.

Have you drawn Free Body Diagrams for both boxes?
If they do not stay together, what can you say about the forces between them?