Need help calculating the tension in the string of two boxes with friction

AI Thread Summary
The discussion revolves around calculating the tension in a cord connecting two boxes, with one box on a table and the other hanging. The user correctly calculated the acceleration of the system as 1.4 m/s² but struggled with determining the tension in the cord. They provided the equations used but noted that their results did not align with the expected answer of 17 N. A key point in the discussion is the correction regarding the mass assignments for the boxes, indicating that the user had them reversed. The conversation emphasizes the importance of accurately applying the equations of motion and friction to solve for tension in such systems.
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Homework Statement



Two boxes are connected by a cord running over a pulley. Box A sits on a table and has a mass of 5.0 kg while box B hangs
freely and has a mass of 2.0 kg. Box A moves to the right and box B moves
downwards. If the coefficient of kinetic friction between box A and the table is
0.20, what is the acceleration of the system and the tension in the cord? You
may assume that the cord remains taut and does not stretch.

Homework Equations


F=ma
fk=mu*Fn


The Attempt at a Solution


The first part is fine i get 1.4m/s2

then the second part to calculate tension I am lost with what to do:

m1g-T=m1a
T-fk=m2a

where m1= 5kg
m2= 2kg

the answer is supposed to be 17N but when i solve for T i don't get anywhere near that...

thanks
 
Physics news on Phys.org
You got your m1 and m2 reversed.
 

Thread 'Errors and significant figures'

I multiplied the values first without the error limit. Got 19.38. rounded it off to 2 significant figures since the given data has 2 significant figures. So = 19. For error I used the above formula. It comes out about 1.48. Now my question is. Should I write the answer as 19±1.5 (rounding 1.48 to 2 significant figures) OR should I write it as 19±1. So in short, should the error have same number of significant figures as the mean value or should it have the same number of decimal places as...
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Thread 'A cylinder connected to a hanging mass'

Thread 'A cylinder connected to a hanging mass'

Let's declare that for the cylinder, mass = M = 10 kg Radius = R = 4 m For the wall and the floor, Friction coeff = ##\mu## = 0.5 For the hanging mass, mass = m = 11 kg First, we divide the force according to their respective plane (x and y thing, correct me if I'm wrong) and according to which, cylinder or the hanging mass, they're working on. Force on the hanging mass $$mg - T = ma$$ Force(Cylinder) on y $$N_f + f_w - Mg = 0$$ Force(Cylinder) on x $$T + f_f - N_w = Ma$$ There's also...
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