Assemble the usual suspects: Draw a diagram showing all the forces acting on the car. Apply Newton's 2nd law to relate the net force to the acceleration. Use kinematics or work/energy to compute the acceleration. (Pick a specific speed: convert 25 mph to m/s.)Narayanswamy said:If a driver traveling down an 8% grade hill slams down the brakes of his car and skids 30 meters, what is the coefficient of friction ( assuming he was traveling at 25 MPH or more)?
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The coefficient of friction is a measure of the amount of resistance between two surfaces in contact. It is a dimensionless number that represents the ratio of the force required to overcome the frictional force to the normal force between the two surfaces.
The coefficient of friction can be determined experimentally by measuring the force required to move an object over a surface at a constant speed and dividing it by the normal force between the two surfaces. It can also be calculated using mathematical models based on the properties of the two surfaces in contact.
There are several factors that can affect the coefficient of friction, including the nature and roughness of the surfaces in contact, the presence of lubricants or contaminants, and the force applied between the two surfaces. Temperature and humidity can also have an impact on the coefficient of friction.
Static friction is the force that must be overcome to set an object in motion when it is at rest on a surface. Kinetic friction, on the other hand, is the force that must be overcome to keep an object moving at a constant speed. The coefficient of static friction is typically higher than the coefficient of kinetic friction.
The coefficient of friction can be reduced by using lubricants between two surfaces, polishing or smoothing the surfaces, or changing the materials of the surfaces to ones with lower friction coefficients. Additionally, reducing the force applied between the two surfaces can also decrease the coefficient of friction.