Static and Kinetic Friction: Find Force & Acceleration

In summary, two blocks, A and B, with masses of 5kg and 10kg respectively, are in contact with each other and a rigid wall on a horizontal surface. The coefficient of friction is 0.15 for both static and kinetic friction. A force of 200N is applied horizontally to block A. The reaction forces between the blocks and the wall are both 200N. When the wall is removed, the acceleration of the system is found to be 11.84ms-2. The equations used were f=ma and fn=uN.
  • #1
phever
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0

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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  • #2
A sketch would help clarify the question please.
 

1. What is the difference between static and kinetic friction?

Static friction is the force that opposes the initial motion of an object, while kinetic friction is the force that opposes the motion of an object already in motion.

2. How is the force of friction calculated?

The force of friction can be calculated using the equation F = μN, where μ is the coefficient of friction and N is the normal force.

3. What factors affect the force of friction?

The force of friction is affected by the type of surfaces in contact, the coefficient of friction between the surfaces, and the normal force acting between the surfaces.

4. How does friction affect an object's acceleration?

Friction acts in the opposite direction of an object's motion, so it can decrease an object's acceleration by reducing the net force acting on it.

5. Can friction ever be completely eliminated?

No, friction can never be completely eliminated as it is a natural force that exists between all surfaces in contact. However, it can be minimized through the use of lubricants or by choosing surfaces with lower coefficients of friction.

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