Forces acting on a two object system using free body diagram

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meaganl
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Homework Statement


threeboxes.gif

A force of magnitude F= 7.30 N pushes three boxes with masses m1= 1.80kg, m2= 3.00kg and m3= 4.20kg, on a level surface.
Draw a free body diagram showing all the individual forces acting on the system consisting of boxes 2 and 3 together. Indicate the directions of the five forces listed below, choosing from vectors A-D in the diagram. If a force does not belong on the FBD, enter N.
directions.gif

i) gravity pulling on box 3
ii) gravity pulling on box 2
iii) box 1 pushing on box 3
iv) floor pushing on box 2
v)floor pushing on box 1

Homework Equations





The Attempt at a Solution



I have tried many solutions like NNNAN, CCNAN,CCNBN and more but it keeps telling that I'm wrong.
 
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You are asked to draw a FBD of the system of blocks 2 and 3 together. The gravity force is always an external force and always present acting down on an object if the object is on earth...it pulls it toward Earth's center. Besides the gravity force, objects are subject to contact forces at the surfaces that touch each other.