# Physics Learning Center

## Physics Olympiads Series Problem 18

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

Problem 18
Given three blocks m1 = 3 kg, m2 = 5 kg and m3 = 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/s2 for the total mass acceleration. Draw all acting forces on each block, apply newton's law.

For m1, the acting forces are F = 20 N and contact force from block 2 to block 1, named Fk12.

Newton's law for block 1: The acting forces of block 2 are Fk21 = 16 N, Fk23, 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 m1, m2 and m3 that are touching each other in a frictionless floor surface. The three blocks being pushed by horizontal force F. Find Fk12, and Fk23 show the answer in F, m1, m2 and m3
Problem source : Fisikastudycenter.com-Modification of Soal Tes Seleksi Olimpiade Fisika Tingkat Kabupaten /Kota Tahun 2011

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