Static and Kinetic Friction: Find Force & Acceleration

AI Thread Summary
The discussion focuses on a physics problem involving two blocks, A and B, with a given mass and coefficient of friction, subjected to a horizontal force. The user calculates the reaction forces when the system is at rest and finds that both blocks exert a force of 200N on each other and on the wall. Upon removing the wall, the user applies Newton's second law to determine the acceleration of the blocks as a system, resulting in an acceleration of approximately 11.84 m/s². The user seeks confirmation on the correctness of their calculations and requests a sketch for better understanding. The thread emphasizes the application of friction and Newton's laws in solving the problem.
phever
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Homework Statement


mA=5kg , mB =10kg , coeff of friction is same for static and kinetic friction = 0.15
g=10ms-2

2 blocks a , b are in contact with each other resting against a rigid wall on a horizontal surface. There is fricition acting between the blocks and the surface . A force of 200N is applied horizontally to A .
a) find reaction forces
b) acceleration if the partition was removed

|_A_||__B__||*-< wall rigid surface

Homework Equations


f=ma , fn=uN


The Attempt at a Solution


since the system is at rest, we assume it has zero acceleration and the reaction force exerted by a on b is 200N and b on wall is 200N .

when wall is removed considering A,B as a system
F=ma
200N - u(Ma+Mb)g = A(Ma+Mb)
200N - 0.15x150 = 15A
200-22.5=15A
177.5=15A
A = 11.84ms-2

please tell me if i have solved the question correctly... some mistake in my method?
 
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A sketch would help clarify the question please.
 

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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