Mass of a block via kinetic friction

In summary: For mass B, use the same x-axis but choose a different y-axis that is perpendicular to the rope. You'll have both T and the weight acting in the x-direction.In summary, the question is asking for the mass of block B in a system where block A (5.9 kg) is connected to block B over a pulley. The angle of the incline is 43° and the coefficient of kinetic friction between block A and the incline is 0.36. The blocks are in motion and the goal is to find the mass of block B. The solution involves setting up equations for the forces in the x and y directions for both blocks and solving for the tension in the rope.
  • #1
AnkhUNC
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0
[SOLVED] Mass of a block via kinetic friction

Homework Statement



In Fig, two blocks are connected over a pulley. The mass of block A is 5.9 kg and the coefficient of kinetic friction between A and the incline is 0.36. Angle θ of the incline is 43°. Block A slides down the incline at constant speed. What is the mass of block B?

http://edugen.wiley.com/edugen/courses/crs1650/art/qb/qu/c06/fig06_34.gif

Homework Equations





The Attempt at a Solution



OK so I'm unsure of how how to compute this question. I'm going to need to find the tension in this problem in order to find the mass of block two correct?

So for m1:
Fy = N-mg+(Tsin43-(Tsin133 [90+43 for the Fk force]*.36))

How do I solve for T here if I don't have a second equation to help me solve? There isn't a normal force on block B seeing as it is in the air so I couldn't impose the two to get rid of N right?

Fx = Tcos(43)-Tcos(133)*.36

Is this correct?

For m2:
Fy = T-mg
Fx = No movement

T>mg or block A would not be in kinetic friction.


Thanks,
 
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  • #2
AnkhUNC said:
So for m1:
Fy = N-mg+(Tsin43-(Tsin133 [90+43 for the Fk force]*.36))

How do I solve for T here if I don't have a second equation to help me solve? There isn't a normal force on block B seeing as it is in the air so I couldn't impose the two to get rid of N right?

Fx = Tcos(43)-Tcos(133)*.36

Is this correct?
This will be a bit easier to analyze using axes that are parallel and perpendicular to the plane, instead of horizontal and vertical.

For m2:
Fy = T-mg
Fx = No movement

T>mg or block A would not be in kinetic friction.
If T > mg, the blocks would accelerate.
 
  • #3
Well that's sort of what I'm trying to do. I'm making the friction and tension south west and north east respectively. I kind of figured the way I set that up was incorrect but I haven't had to do two forces at the same time before.
 
  • #4
For mass A, choose your x-axis as parallel to the incline and your y-axis as perpendicular. Then only the weight will need to be broken into components.
 

Related to Mass of a block via kinetic friction

What is the mass of a block via kinetic friction?

The mass of a block via kinetic friction refers to the amount of matter contained in the block that is being measured through the force of friction acting on it. It is typically measured in kilograms (kg).

How is the mass of a block via kinetic friction calculated?

To calculate the mass of a block via kinetic friction, you will need to know the force of friction acting on the block and the coefficient of kinetic friction for the surface the block is on. The formula for calculating mass using these values is: mass = force of friction / coefficient of kinetic friction.

What is the coefficient of kinetic friction?

The coefficient of kinetic friction is a dimensionless number that represents the amount of friction between two surfaces in contact when one surface is in motion. It is typically denoted as "μ" and can range from 0 (no friction) to 1 (high friction).

How does the mass of a block affect its kinetic friction?

The mass of a block directly affects its kinetic friction. The greater the mass of the block, the greater the force of friction needed to move it. This is because a heavier block has more inertia and therefore requires a greater force to overcome it.

What factors can affect the mass of a block via kinetic friction?

Aside from the force of friction and coefficient of kinetic friction, the mass of a block can also be affected by external factors such as the type of surface the block is on, the temperature, and the presence of any lubricants or contaminants on the surface.

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