#### Group 4 Friction Lab - did Johnny slip from the roof or was he pushed?

Group 4: Coefficient of Kinetic Friction Scenario Pronounced dead at the scene of the crime, poor Johnny is found lying face up on the dance floor, perhaps slipped from his rooftop to the unforgiving stiff dance floor below. Would such a fall have been possible? Or was young Johnny a victim of foul play? The coefficient of kinetic friction is an experimental value which we calculated and compared to values calculated by independent researchers. The ability of the fall to take place is the net force acting upon Johnny, after the subtraction of the force of friction. If this force is greater than zero, such a fall is possible, and becomes more probable as the value of the force increases Given that Johnny's mass and the pitch of the roof are known, all that is left to discover is the coefficient of kinetic friction. This simple experiment involves dragging one material across another, and measuring the minimum amount of force required to do this at a constant velocity. The materials we used were rubber, the same sort found in Johnny's shoes, and a wet asphalt shingle, of the same variety found on Johnny's roof. Our experiment gave us a value of 0.3 for the coefficient of kinetic friction between rubber and wet asphalt, one which was consistent with researched results. Calculations These calculations require vector analysis, all of which is based upon the diagram below.

• Word count: 468
• Level: International Baccalaureate
• Subject: Group 4 Projects