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Physics Olympiads Series Problem 13

Physics.fisikastudycenter.com, Physics Olympiads problem series, olympiads preparation for beginner level, high school level. The needed basic concepts for this problems are forces (weight, frictional force, string tension), Newton's Laws.

Problem 13
Given three masses: mA = 40 kg, mB, dan mC = 50 kg. The static frictional force coefficient between A and B is 0.3, between A the table is 0,2. See the figure!



Calculate the minimum mass of B so the system remains rest!
Question source: Fisika Study Center-Modification of UMPTN 1994 / Indonesian colleges examination entrance


Solution
Sketch the forces:



Analyze mC that is in equilibrium conditions, both x axis and y axis, so then, ΣF = 0



mB is in equilibrium conditions too, then ΣFx = 0



Analyze mA, apply equilibrium conditions to find the result:



Try This!
Given three masses that are mA = 20 kg, mB, dan mC = 25 kg. The static frictional force coefficient between A and B is 0.3 and between A and the table is 0.2, see the figure!



Find the minimum mass of B, so that the system remains at rest!
Question source: Fisika Study Center-Modification of UMPTN 1994

answeri: 105 kg
prepared by : Fisika Study Center
Literatures/sources:
-UMPTN 1994 Questions
-tofi.or.id

 

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