Understanding Friction: Static and Kinetic, Coefficients, and Applications, Slides of Physics

Download Understanding Friction: Static and Kinetic, Coefficients, and Applications and more Slides Physics in PDF only on Docsity! Friction Docsity.com Holding in Place  Objects on an incline will often stay put.  There must be a force that holds the object in place.  Static friction is from the contact of resting objects. • Force holds up to a certain point • Force is based on the type of contact (rough, smooth) • Maximum force is proportional to the pressing force of the object (normal force) Docsity.com Slippery Slope  If Ffr < sFN = smg cos then the block will hold.  At equality the block just begins to move.N F  mgFg cosmg sinmg sin(max) mgFfr     tan cossin    s s Nsfr mgmg FF Docsity.com Sliding  Sliding objects also have a frictional force exerted on them.  This frictional force is kinetic friction.  An approximate formula: k is the coefficient of kinetic friction Nkfr FF  Docsity.com Static vs. Kinetic  Static and kinetic friction are similar. • Force in opposite direction to motion • Proportional to normal force • Coefficient of friction depends on materials  Static and kinetic friction are different. • Static friction is an inequality up to a maximum • Coefficient of friction is typically greater for static friction at the same surface • Wood on wood (0.4 vs. 0.2) Docsity.com Minimum Sliding  When the skier is sliding slowly we can neglect air resistance.  Kinetic friction balances the component of gravity pulling forward. ° Fgx = mg sin FN = mg cos Ffr = -kFN 05.0tan cossin 0      k k frgx mgmg FF Docsity.com Normal Force and Friction  Friction depends on both the normal force and on the coefficient of friction.  To reduce friction requires reducing one of those factors. • Reduce normal force by lightening the load • Reduce normal force by adding additional upward force • Add a lubricant to reduce the coefficient of friction Docsity.com