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Physics Olympiads Series Problem 19

Fisikastudycenter.com,- Physics Olympiads Problems Series, Question #19, newton's law, mechanics, system acceleration, for beginner.

Problem # 19
Given three blocks m1 = 3 kg, m2 = 5 kg and m3 = 2 kg being pushed across a frictionless floor by force F = 75 N shown in figure below. The slope has θ = 37° .



Find the contact force between the block 1 and block 2, use sin 37 ° = 3/5 and the acceleration due to gravity g = 10 m/s2 !
Problem source : Fisikastudycenter.com-Modifikasi Soal Tes Seleksi Olimpiade Fisika Tingkat Kabupaten /Kota Tahun 2011


Discussion
Find the system acceleration first, we got the acceleration a = 1,5 m/s2.

The forces that are acting on the block 1 : W (weight of block) and its components at x and y axis, W1 = m1 g = 30, W1 sin θ dan W1 cos θ, F, normal force, contact force 1 and 2, named Fk12 :



Newton's law for block 1



The block 2:



Newton's law for block 2:



The block 3:



Applying newton's law on block three, the result should be 15 N, as the previous calculation



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