## Physics Olympiads Series Problem 19

- Category: Olympiads
- Written by fisikastudycenter

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

**Problem # 19**

Given three blocks m_{1} = 3 kg, m_{2} = 5 kg and m_{3} = 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/s^{2} !

**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/s^{2}.

The forces that are acting on the block 1 : W (weight of block) and its components at x and y axis, W_{1} = m_{1} g = 30, W_{1} sin θ dan W_{1} cos θ, F, normal force, contact force 1 and 2, named Fk_{12} :

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

**prepared by:**

Fisikastudycenter.com