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Free Body Diagrams: Static Equilibrium 
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#1
Feb310, 09:30 PM

P: 3

1. The problem statement, all variables and given/known data
Blocks A & B each have mass 5kg, and all contact surfaces are frictionless. Determine the force F needed to keep the blocks in static equilibrium, and the forces on all contact surfaces. 2. Relevant equations I know I need to find where Fx= 0 and where Fy= 0. 3. The attempt at a solution Fx = Fcos20 Fy= Fsin20  5 kg Am I even close? 


#2
Feb410, 03:00 AM

HW Helper
P: 4,435

Hi hunter007, welcome to PF.
When you apply force F to the systemis, the acceleration of the system is a = F/(Ma + Mb)..........(1). It is parallel to the ground. Since block A is not attached to the block B, due the inertia, it will experience an equal and opposite acceleration. The block A will remain rest when component of the weight of the block A balances the component of the acceleration. Equate these components and find a. Put this value in equation(1) to get F. 


#3
Feb410, 10:54 AM

P: 3

Could you explain a little more on how to get a? Once I find that I could find F.



#4
Feb410, 11:26 AM

HW Helper
P: 4,435

Free Body Diagrams: Static Equilibrium
mg*sinθ = a*cosθ.
Find a. 


#5
Feb410, 12:48 PM

P: 3

a = 5(9.8)*tan(30)
= 28.3 F= 28.3(5+5) = 283 N. Did I do it right? 


#6
Feb410, 07:15 PM

HW Helper
P: 4,435

The given angle is 20 degrees.



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