Kinetic friction incline problem

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SUMMARY

The discussion centers on calculating the tension in a rope used to pull a sled with a mass of 75 kg at a constant velocity on a horizontal surface, considering a coefficient of kinetic friction (μk) of 0.10 and a pulling angle of 42 degrees. The net force equations were established for both the x and y directions, leading to the formula Fτ = μk * mg / cos(42) + μk * sin(42). The final calculated tension in the rope is approximately 91 N. The algebraic evaluation of the cosine and sine functions was highlighted as a potential source of error in the calculations.

PREREQUISITES
  • Understanding of Newton's laws of motion
  • Familiarity with the concepts of kinetic friction and its coefficient
  • Basic trigonometry, specifically sine and cosine functions
  • Ability to solve algebraic equations involving multiple variables
NEXT STEPS
  • Review the principles of Newton's second law and its application in friction problems
  • Study the effects of different angles on tension in pulling scenarios
  • Learn about the calculation of forces in two dimensions
  • Explore advanced topics in dynamics, such as friction in non-horizontal surfaces
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Students in physics, particularly those studying mechanics, as well as educators and anyone interested in solving problems related to forces and friction in real-world applications.

Nirupt
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Homework Statement


Mildred pulls a sled loaded with beer along a horizontal surface at constant velocity, as Bubba told her he needed it for he and his buddies to watch the football game. If the sled and beer in it has mass = 75 kg, the coefficient of kinetic friction μk between the runners and the snow is 0.10, and she is pulling a rope inclined at an angle of 42 degrees, what is the magnitude of the tension in the rope?

Homework Equations





The Attempt at a Solution



X direction:

μκ = .1

Fκ = .1*Fn


ƩFnetχ = Fτ*cos(42) - μκ*Fn = 0


ƩFnety = Fn + Fτ*sin(42) - mg = 0
Fn = -Fτ*sin(42) + mg

so I plug this for Fn

Fτ*cos(42) - μκ*(-Fτ*sin(42) + mg) = 0

Fτ*cos(42) + μκ*Fτ*sin(42) - μκ*mg = 0
Fτ = μκ*mg/cos(42) + μκsin(42)
Fτ = .1*735/(cos(42) + .1*sin(42))
Fτ = 73.5/.0669
Fτ = 90.7504
F ≈91N

Just checking to make sure this is correct. I feel like I messed up my algebra with Fτ.. I mean.. would it be 2Fτ or Just Fτ like I have it. I feel like basic algebra can be kind of overwhelming at time.
 
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Your working looks correct until you evaluated (cos(42) + .1*sin(42)). cos(42deg) > cos(45deg) = sqrt(2)/2 > .7.
 

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