## Physics Olympiads Series Problem 18

- Category: Olympiads
- Written by fisikastudycenter

Fisikastudycenter.com, Olympiads Problems Series in mechanics, newton's second law, forces, acceleration, physics olympic events preparation for beginner.**Problem 18**

Given three blocks m_{1} = 3 kg, m_{2} = 5 kg and m_{3} = 2 kg being pushed across a frictionless floor by horizontal force F = 20 N shown in figure below.

Find the contact forces that are acting on each block!

**Problem source** : Fisikastudycenter.com-Modification of Indonesian Physics Olympiad Selection Test - District Level Year 2011

**Discussion**

Find the acceleration of total mass first, as shown in problem 16, we got 2 m/s^{2} for the total mass acceleration. Draw all acting forces on each block, apply newton's law.

For m_{1}, the acting forces are F = 20 N and contact force from block 2 to block 1, named Fk_{12}.

Newton's law for block 1:

The acting forces of block 2 are Fk_{21} = 16 N, Fk_{23}, to the left.

The calculation result for block 3 has to be equal with previous calculation (4 N.

**prepared by**:

Fisika Study Center

**Try This!**

Given three blocks m_{1}, m_{2} and m_{3} that are touching each other in a frictionless floor surface.

The three blocks being pushed by horizontal force F. Find Fk_{12}, and Fk_{23} show the answer in F, m_{1}, m_{2} and m_{3}

** Problem source :** Fisikastudycenter.com-Modification of Soal Tes Seleksi Olimpiade Fisika Tingkat Kabupaten /Kota Tahun 2011