Stopping distance of an automobile skidding on dry and wet pavement

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Homework Help Overview

The discussion revolves around calculating the stopping distance of a 1500-kilogram automobile skidding on both dry and wet pavement. The original poster presents a scenario involving an emergency stop while traveling at 90 km/h, and seeks to determine the stopping distances under different conditions.

Discussion Character

  • Exploratory, Assumption checking, Problem interpretation

Approaches and Questions Raised

  • Participants inquire about the completeness of the provided data and the necessity of showing work before assistance can be given. There are discussions about the coefficients of friction for dry and wet pavement, and how to apply the forces involved in the problem. Some participants suggest using conservation of energy as a potential approach to relate kinetic energy to frictional force.

Discussion Status

The discussion is ongoing, with participants exploring various interpretations of the problem and questioning the assumptions made. Some guidance has been offered regarding the use of frictional forces and energy conservation, but no consensus or resolution has been reached.

Contextual Notes

Participants note the requirement to show working in homework submissions and the specific coefficients of friction provided for the materials involved. There is an emphasis on understanding the forces at play and how they relate to the stopping distance.

msesulka
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A 1500-kilogram automobile travels at a speed of 90 km/h along a straight concrete highway. Faced with an emergency situation, the driver jams on the brakes , and the car skids to a stop. What will the stopping distance be for (a) dry pavement and (b) wet pavement?
 
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In future could you please post your homework questions in the homework forums, thanks.

With respect to this question, what are your thoughts? What have you attempted? Is this all the data given in the question?
 
This looks like homework. If it is, please note that you are required to show working before we can help; so, what are your thoughts?

N.B. In future, please post in the homework forum.
 
sorry about that i don't really know how to get around on this site really. So far i know that the given coefficiants of kinetic friction for rubber on dry concrete is 0.85 and for rubber on wet concrete is 0.60. I know you somehow have to add all the forces in the problem using F=(m)(g) and F=(m)(a) but i don't know how to get those components
 
F=mg gives the weight of the truck. Do you know the equation F=\muR, where \mu is the coefficient of friction, and R is the normal contact force. This gives you the force of friction.
 
Yea I actually have that formula. So would I find the force of friction for the wet pavement and then the force of friction for the dry pavement? Then how would I incorporate those answers into finding the stopping distance?
 
Try using conservation of energy. To start the car has kinetic energy, at the end it has zero (since it's at rest). How can you relate this change in energy to the frictional force?
 

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