Mechanics midterm-terminal velocity question

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SUMMARY

The discussion focuses on calculating the terminal velocity of a boy sliding on a water sliding bed, considering both kinetic friction and water resistance. The forces involved include gravitational force, kinetic friction (μ), and water resistance (F(v) = -cv). The user has derived the equation -mgsin(θ)μ - cv = mdv/dt but is seeking assistance with integration to find the terminal velocity, which is expected to exhibit an exponential decay behavior over time.

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  • Understanding of Newton's second law of motion
  • Familiarity with concepts of kinetic friction and its coefficient (μ)
  • Knowledge of water resistance modeling (F(v) = -cv)
  • Basic calculus skills for integration
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  • Study the derivation of terminal velocity in fluid dynamics
  • Learn about integrating differential equations in physics contexts
  • Explore the effects of different coefficients of friction on motion
  • Investigate the relationship between gravitational forces and inclined planes
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Kara-Mustafa
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1. A boy is sliding on the water sliding bed. The angle between sliding bed and the horizontal is θ(theta). When the coefficient of the kinetic friction is μ(COF) and when the wate resistance is F(v)=-cv, obtain the terminal velocity. (two frictions - for this i don't know whether it means linear friction+quadratic friction or something else)



3. But anyway, so far I reached this point:

F-force due to gravity
F(v) - force due to water resistance

F*μ+F(v)=mdv/dt

-mgsin(θ)μ-cv=mdv/dt

dt=mdv/mgsin(θ)μ -cv

And I'm stuck right here. Are my workings so far correct? Can you show me how to integrate this function and find terminal velocity. I know it's going to have exponential term which will drop to zero after sufficient time.
 
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Hi Kara-Mustafa!Welcome to PF! :smile:

You're confusing the friction (µN) with the downhill component of the gravitational force …

you need both :wink:
 

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