How much work done by friction when a box w/apparent mass...?

In summary: This will give you a different answer than before, but it should be correct.In summary, the problem involves finding the work done by friction on a box with an apparent mass of 325kg, moving horizontally across a floor with a coefficient of friction of .33 and being pulled at a 59.9 degree angle for 2.60m. The force pulling the box can be calculated using the formula Fa= umg/(usin@ + cos@). The concept of apparent weight was used to find the correct force applied.
  • #1
jmm5180
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Homework Statement


How much work is done by friction when a box with an apparent mass of 325kg moves horizontally across a floor with coefficient of friction of .33 and is pulled at 59.9 degree angle for 2.60 m? What is the force that is pulling the box?

Homework Equations


W=Fdcos@ (@= theta)
Fnet=ma

The Attempt at a Solution


I searched for what apparent mass was, but what I found seemed to do with volume and water displacement, which aren't related to this problem. Instead I tried solving the second question first because I needed Normal force to solve the work done by friction.

For my free body diagram, I had force applied (Fa) in the y direction upwards on the y-axis along with normal force. Along the negative y-axis I had weight. Force of friction (Ff) was along the negative x axis, and force applied in the x direction was on the positive x axis.

In the x direction...
Ff=Facos@ (since no acceleration)
uN = FaCos@

In the y direction...
Fasin@ + N = W (again since no acceleration)
N= mg - FaSin@

So plugging in,,,
u(mg-Fasin@) = FaCos@

Solving for Fa I got...
umg-uFasin@ = Facos@
Fa= umg/(usin@ + cos@)
Fa= (.33*325 kg*9.8)/(.33sin59.9+cos59.9)
Getting that the force applied = 1335.50 N, but this is not correct.

Any help would be appreciated, thanks in advance.
 
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  • #2
I found this on a Google search:
In physics, apparent weight is a property of objects that corresponds to how heavy an object is. The apparent weight of an object will differ from the weight of an object whenever the force of gravity acting on the object is not balanced by an equal but opposite normal force.
 
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  • #3
If you assume ##apparent \ weight = mg - N## do you see a way to proceed?
 
  • #4
anlon said:
If you assume ##apparent \ weight = mg - N## do you see a way to proceed?
Yes, thank you!
 
  • #5
Try taking the apparent weight = N.
 

1. How is friction related to work?

Friction is a force that acts in the opposite direction of motion, which means that it can do negative work. This means that when an object is moving due to a force, friction will act in the opposite direction and remove some of the energy that was put into the object.

2. What is meant by "apparent mass" in this context?

Apparent mass is a term used to describe the effective mass of an object in a given situation. In the case of a box being moved across a surface, the apparent mass would take into account the weight of the box, as well as any additional forces acting on it, such as friction.

3. How does the weight of the box affect the work done by friction?

The weight of the box will affect the work done by friction because it determines the normal force between the box and the surface it is being moved across. The greater the weight of the box, the greater the normal force, and therefore, the greater the friction force. This means that more work will be done by friction to oppose the motion of the box.

4. Is work done by friction always negative?

No, work done by friction can be either positive or negative depending on the situation. If the motion of the object is in the same direction as the friction force, then the work done by friction will be positive. However, if the motion of the object is in the opposite direction of the friction force, then the work done by friction will be negative.

5. How can the work done by friction be calculated?

The work done by friction can be calculated by multiplying the magnitude of the friction force by the distance the object moves against the force. This can be represented by the equation W = Ff * d, where W is the work done, Ff is the friction force, and d is the distance moved against the force.

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