Long desk with one end cut, falls from the other one

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SUMMARY

The discussion revolves around a physics problem involving a desk with one end cut at a 45-degree angle, requiring the calculation of the final velocity of a second desk resting beneath it. Key concepts include the moment of inertia of a thin long rod, represented by the formula Io = 1/12ml², and Newton's second law (F=ma). The participant struggles with applying these concepts to the problem, particularly in utilizing the moment of inertia effectively. The suggestion is made to consider conservation laws to simplify the approach to finding the solution.

PREREQUISITES
  • Understanding of Newton's second law (F=ma)
  • Knowledge of moment of inertia for thin long rods (Io = 1/12ml²)
  • Familiarity with conservation laws in physics
  • Basic principles of kinematics
NEXT STEPS
  • Study the application of conservation of momentum in collision problems
  • Learn about rotational dynamics and how moment of inertia affects motion
  • Explore examples of kinematic equations in physics
  • Review problem-solving strategies for complex mechanics problems
USEFUL FOR

Students studying physics, particularly those focusing on mechanics and kinematics, as well as educators seeking to clarify concepts related to moment of inertia and conservation laws.

korec123
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Sorry for my english at the beginning. :) I am not really into academic(physic) english.
1. Homework Statement
Picture of problem : http://screenshot.sh/ouZAbUeL9Qzmj

We have got a desk,mass m1, length L1 and thickness d, and L1>>d. One of it's ends is angled by 45 degree. At the beginning it is put on the other desk which thickness is also d and mass is m2.
I have to find final velocity of the second desk, this one which is lying on the table.
We skip friction.
I also have information at the end of the task that Moment of inertia of thin long rod, length l, and mass m is 1/12ml^2.

Homework Equations


Io=1/12ml^2
F=ma.

The Attempt at a Solution


I don't really have any idea how to approach this task. What i could is just simply mark all the forces, just what i do every time when i do this kind of question (i mean, i have some mass and i have to find accelerate, whole basically based on 2nd Newton law's), but it didnt help.
I ve only found that sin of the angle between first desk and the table is sin=d/L1-d.
The biggest problem i think is that i don't know how to use info about moment of inertia in this question.

If you can explain to me, how to approach this one and how to use moment of inertia i would be grateful.
Thanks in advance,
 
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korec123 said:
how to approach this one
With kinetics problems, your first thought should be whether you can avoid having to deal with forces by using conservation laws. What conservation laws apply here? Might these get you to the answer?
 

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