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Friction -

Friction - . TWO TYPES. Static Friction- . Kinetic Friction-. Coefficient of Friction. An 800N skier skies on level ground. How much force doe the skier need to exert to move forward at a constant velocity?.

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Friction -

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  1. Friction - TWO TYPES Static Friction- Kinetic Friction- Coefficient of Friction

  2. An 800N skier skies on level ground. How much force doe the skier need to exert to move forward at a constant velocity? How much force would the girl need to exert to get a 25kg rubber tire to start in motion on dry asphalt?

  3. Example:A college student pushes a heavy box across the floor into her dorm room. She notices it takes 50N of force to get the box to start to move. What is the force of static friction? What is the weight of the box if the coefficient of static friction is .5? Once the girl starts the box in motion, she notices it is easier to keep moving. If the coefficient of kinetic friction is .3, how much kinetic friction is present? d) If the girl pushes with the same 50N of force, what will be the acceleration of the box? e) Complete the FBD of the box as it accelerates.

  4. Activity:Given the materials provided at your table. Determine the coefficient of static and kinetic friction between the table top and the wooden box. Follow Up Question: Which situation would cause the greater amount of friction when being pulled at a constant velocity? Both blocks have the same mass. v v

  5. Anti-lock braking system (ABS) is an automobile safety system that allows the wheels on a motor vehicle to maintain tractive contact with the road surface according to driver inputs while braking preventing the wheels from locking up (ceasing rotation) and avoiding uncontrolled skidding Example:Sliding Friction vs. Rolling Friction A tired driver notices that the car in front of him has suddenly stopped. The driver slams on the breaks in an attempt to not crash into the other car. The 1000kg car was going 20m/s when the driver slammed on the breaks … If the car did not have anti-lock breaks and the rubber tires locked causing the car to skid on dry asphalt, what friction would be present to stop the car? What would be the deceleration of the car under these conditions? If the stopped car was 27m in front of the drivers car at the moment of braking, does he crash into the other car? Would the driver crash if he had anti-lock brakes?

  6. Incline Plane – All of Newton’s Law apply.. We simply make use of geometry to adapt the situation Ex: A 5kg wooden crate initially at rest sits on a frictionless incline set at 35°… What is the normal force acting on the crate? What is the net force acting on the crate? What will be the acceleration of the crate down the incline? If friction is considered and the wooden crate started from rest on a wooden incline, what frictional force opposes the motion? What would be the acceleration under the conditions in part ‘d’? θ

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