Static friction on a car on a circle

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Homework Help Overview

The discussion revolves around the dynamics of a car moving on a circular track that is sloped away from the center. Participants are exploring the role of static friction in maintaining the car's circular motion at a constant speed, particularly in relation to the forces acting on the car due to the slope of the track.

Discussion Character

  • Conceptual clarification, Problem interpretation, Assumption checking

Approaches and Questions Raised

  • Participants are attempting to understand the direction of static friction in the context of circular motion and slope. Questions are raised about how static friction interacts with gravitational and normal forces to provide the necessary centripetal force.

Discussion Status

The discussion is ongoing, with participants offering insights into the relationship between speed, slope angle, and the forces involved. Some guidance has been provided regarding drawing free body diagrams and setting up equations to analyze the forces, but no consensus has been reached on the direction of static friction.

Contextual Notes

Participants are working with specific values: a speed of 20 km/h, a radius of 113 m, and a slope angle of 8 degrees. The implications of these parameters on the forces are under consideration.

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When a car is moving on a circular track which is sloped away from the centre of the track, is the static friction keep that car on the circle (constant speed) towards the outside of the circle, opposite the acceleration?

I'm having trouble seeing this because to me, the car would want to fall out of the circle, because of the slope. Which would mean it would need the static friction to be towards the centre.
 
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The static friction can act in both directions, towards the centre and away from it. To move along the circle with speed v, the car needs proper centripetal force, which is the resultant of gravity, normal force and static friction between the road and tyres.

ehild
 
OK but in this case which direction would the static friction be? I just need to know to draw the free body diagram.
 
It depends on the speed of the car, the radius of circle and the angle of the slope.
 
The speed is 20 km/h, the radius is 113m and the angle of the slope is 8 degres
 
Draw the free body diagram. You have two unknown forces: the normal force and the static friction. The normal force is perpendicular to the road, the friction is parallel, but you do not know if it points inward or outward. The resultant has to be horizontal, pointing towards the centre and equal to mv2/R. Write the equations for the force components, horizontal and vertical, assuming a direction for the friction. There are two equations with two unknowns. If you get negative result for the friction it points to the other direction you assumed.

ehild
 

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