Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
• Targets • • • define what causes friction Do Now • • calculate the different states of friction put solutions to homework on board Homework • • p. 141; Practice E; 1-4 Experiment 4.3 informal report Static Friction • the force that resists the initiation of sliding motion between two surfaces that are in contact and at rest Kinetic Friction • the force that opposes the movement of two surfaces that are in contact and are sliding over each other Frictional Forces • oppose the direction of motion (kinetic) • provide equilibrium (static) • parallel to the surface • proportional to the normal force • due to electrostatic forces between atoms Coefficient of Friction • the ratio of the magnitude of the force of friction between two objects in contact to the magnitude of the normal force with which the objects press against each other •μ •μ k = Fk / Fn s = Fs,max / Fn • Pyro’s blast knocks Iceman, whose mass is 90 kg, down and he slides backwards across the frozen lake with an initial velocity of 11 m/s. Assume Iceman is made of ice (μk for ice on ice is 0.03). How long does it take Iceman to stop sliding backwards if the only force acting upon him is friction?