Finding the angle of an inclined plane

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SUMMARY

The discussion centers on calculating the angle θ of an inclined plane where a sled slides down at a constant velocity, factoring in kinetic friction with a coefficient μk of 0.050. The user derived the equation tanθ = μ, leading to an angle of approximately 2.7° or 2.9°, which was perceived as too small. The response clarified that the perceived angle is reasonable given that the static friction coefficient is higher (0.1-0.15), indicating that the sled likely required an initial nudge to start sliding.

PREREQUISITES
  • Understanding of Newton's laws of motion
  • Knowledge of friction coefficients, specifically kinetic and static friction
  • Familiarity with trigonometric functions, particularly tangent and arctangent
  • Ability to draw and interpret force diagrams
NEXT STEPS
  • Study the differences between static and kinetic friction coefficients
  • Learn about the application of Newton's laws in inclined plane problems
  • Explore advanced topics in dynamics, such as forces on inclined planes with varying friction
  • Investigate the effects of initial conditions on motion down an incline
USEFUL FOR

Students in physics, educators teaching mechanics, and anyone interested in understanding motion on inclined planes and the effects of friction.

Mitza
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So here's the problem:

A sled slides down a long snow-covered slope that is at an angle θ to the horizontal. Kinetic friction acts on the sled as it slides where the kinetic coefficient of friction between the sled and snow is μk = 0.050. Ignore air-resistance when solving this problem.

If we observe the sled to be traveling at a constant velocity, what is θ? (in degrees)

So far I've drawn a force diagram and done this;
∑F= ma
∑F= 0
mgsinθ - μmgcosθ = 0
mgsinθ = μcosθ
tanθ = μ
arctanμ = θ

I know I've done something wrong because with that working the final angle is 2.9° which seems far too small.

Thanks in advance for any help!
 
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Mitza said:
So here's the problem:

A sled slides down a long snow-covered slope that is at an angle θ to the horizontal. Kinetic friction acts on the sled as it slides where the kinetic coefficient of friction between the sled and snow is μk = 0.050. Ignore air-resistance when solving this problem.

If we observe the sled to be traveling at a constant velocity, what is θ? (in degrees)

So far I've drawn a force diagram and done this;
∑F= ma
∑F= 0
mgsinθ - μmgcosθ = 0
mgsinθ = μcosθ
tanθ = μ
arctanμ = θ

I know I've done something wrong because with that working the final angle is 2.7° which seems far too small.

Thanks in advance for any help!
Your answer is correct.
It probably seems too shallow because the static coefficient is a lot higher, more like 0.1-0.15. So you have to assume the sled was given a nudge to get it started.
 
haruspex said:
Your answer is correct.
It probably seems too shallow because the static coefficient is a lot higher, more like 0.1-0.15. So you have to assume the sled was given a nudge to get it started.
Okay thank you for your response!
 

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