Connected Blocks HeLP!!

S_fabris

I have two questions reguarding connected blocks (that are driving me crazy):
1. Two blocks in contact with each other move to the right across a horizontal surface(frictionless). Determine the magnituede of the force exerted on the 2.2kg block by the 8.2kg block.

--81N-->[2.2kg][8.2kg]<--13N--


2. Three blocks are on a frictionless horizontal surface. The blocks are connected by strings (massless) with tensions T1 and T2. Calculate tension T1

<--9.2--[3kg]--T1--[1kg]--T2--[5kg]--38N-->

ANY help with either one of these questions is greatly appreciated...i have tried a few times with both of the problems and i dont have many tires left on the homework server

Thank you,
Sergio

PhanthomJay

Look at the entire system. What is the NET external force acting on the system of blocks? What does Newton's 2nd law say about the acceleration of the system of blocks? Will each individual block accelerate at that same rate? Examine the forces acting on each of the blocks separately in a free body diagram. What is the magnitude and direction of the contact or tension force between the blocks? Does Newton's 3rd law come into play here?

S_fabris

well for the first problem...i tried 81N-63N for the total force exerted on bloc and found the acceleration by adding the masses. then i used that acceleration multiplied by 8.2kg to find the force (got 53.63N) but thats wrong. I did take into consideration all the things you have said and im still stuck...perhaps helping me by suggesting an equation (all the ones i have tried have failed)

OlderDan

Is that red 63 supposed to be 13? That's what you had in youur first post. The 53.63N is not wrong, it's just not the force you were asked to find. Think about what you calculated and how it is related to what you were asked to find.