Solve Free Body Diagram: 2 Boxes, m1=35kg, m2=45kg

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SUMMARY

The discussion focuses on solving a physics problem involving two boxes with masses m1=35kg and m2=45kg, suspended from a rope over a rigid horizontal rod. Participants emphasize the importance of drawing accurate free body diagrams (FBD) for each mass to apply Newton's second law effectively. The key equations discussed include Fnet=ma and Fnet=FT - Fg, which are essential for determining the acceleration of the boxes, the tension in the rope, and the displacement after 0.5 seconds. A consistent sign convention is recommended for clarity in calculations.

PREREQUISITES
  • Understanding of Newton's laws of motion
  • Ability to draw and interpret free body diagrams (FBD)
  • Familiarity with basic kinematic equations
  • Knowledge of forces including tension and gravitational force
NEXT STEPS
  • Learn how to construct free body diagrams for complex systems
  • Study the application of Newton's second law in multi-body systems
  • Explore kinematic equations to calculate displacement and acceleration
  • Investigate the effects of friction in pulley systems
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Students studying physics, particularly those focusing on mechanics, as well as educators looking for examples of problem-solving techniques in dynamics involving multiple masses and forces.

cindy!
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Homework Statement



Two boxes of masses m=35kg and m2=45kg, are hung vertically from opposite ends of a rope passing over a rigid horizontal metal rod. They system starts moving from rest. Assuming that friction between the rod and the rope is negligible, determine the magnitude of
(a) the acceleration of the boxes
(b) the tension in the rope
(c) the magnitude of each box's displacement after 0.5s

Homework Equations



Fnet=ma
Fnet= FT - Fg
ma=FT-Fg

(well i think this is right, depending on how the free body diagram is drawn..)


The Attempt at a Solution



Well...I have no idea what the question is saying, I am unsure how to draw the actual diagram and also how to draw the FBD. This is how i inteperted it:

2dtzqs5.jpg


4bso6zq.jpg
 
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maybe I am reading it wrong, but the way i read it was that there are 2 boxes tied to each other with a rope and that rope is hung on an iron bar.
 
What's F_R in your diagram?? I agree with fizz on the interpretation of the problem.
 
I assume you are to treat this just as you would if the rod were a frictionless (and massless) pulley. Draw a free body diagram for each mass separately.

Apply Newton's 2nd law to each mass (just like in your equations) to get two equations, which you'll solve together. Hint: Adopt a consistent sign convention, for example: up is positive and down is negative. Let "a" be the magnitude of the acceleration; how do the accelerations of the masses relate to each other?
 

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