Friction.

Slides:

Advertisements

Similar presentations

Module 4, Recitation 3 Concept Problems, Friction.

Advertisements

Applications of Newton’s Laws

Friction Friction Problem Situations

When a car accelerates forward on a level roadway, which force is responsible for this acceleration? State clearly which.

Sliding Friction A force that opposes motion Acts parallel to the

Friction Friction is a force that opposes the motion, or tendency of motion, of an object. Friction is caused by the electromagntic interactions of particles.

Copyright © 2007, Pearson Education, Inc., Publishing as Pearson Addison-Wesley. Equilibrium Using Newton’s second law Mass, weight, and apparent weight.

Newton’s Laws of Motion Problems MC Questions

as the force required before you changed the crate’s orientation.

Friction Friction is a force that opposes the motion, or tendency of motion, of an object. Friction is primarily caused by the chemical bonding of molecules.

FRICTION SLEDS, SANDPAPER, AND LOTS of SLIDING. Friction Any force that resists motion It involves objects that are in contact with each other. This is.

Physics. Session Opener A recent space shuttle accident occurred because of failure of heat protecting devices. How was this heat generated ?

A 6. 0-kg object undergoes an acceleration of 2. 0 m/s2

EVERY-DAY FORCES Force of gravity Normal force Force of friction Universal force of gravity.

Week.  Student will:  Incorporate Force of Friction into calculation  Static Friction  Kinetic Friction.

21. ConcepTest 4.11On an Incline 21. ConcepTest 4.11 On an Incline 1) case A 2) case B 3) both the same (N = mg) 4) both the same (0 < N < mg) 5) both.

1 Some application & Forces of Friction. 2 Example: When two objects of unequal mass are hung vertically over a frictionless pulley of negligible mass,

Chapter 6 Applications of Newton’s Laws What keeps Leo in his seat when the train stops?

AP Physics C I.B Newton’s Laws of Motion. The “natural state” of an object.

Chapter 5 THE LAWS OF MOTION. Force, net force : Force as that which causes an object to accelerate. The net force acting on an object is defined as.

Physics Vectors and Forces in Two Dimensions. Problem #1 A plane is flying at a velocity of 95 m/s west and encounters a wind of 25 m/s to the south.

Free Body diagrams and problem solving

Multiple Object Systems 1. Analyze the system as one object. 2. Analyze each object individually. 3. Create multiple equations to solve for multiple unknowns.

Aim: How do we explain the force of friction?. Visualizing Friction.

4.9 Static and Kinetic Frictional Forces There are situations where friction helps us and at other times it is a hindrance. Advantages of friction: Disadvantages.

An 7.3-kg object rests on the floor of an elevator which is accelerating downward at a rate of 1.0 m/s 2. What is the magnitude of the force the object.

Friction Dynamics Physics. #1) Friction of a car A car has a mass of 1700 kg and is located on a level road. Some friction exists in the wheel bearings.

Friction Dynamics Physics. #1) Friction of a car A car has a mass of 1700 kg and is located on a level road. Some friction exists in the wheel bearings.

Period 2 Question 1.

Friction. I. Friction A. Background 1. A force that acts opposite the direction of movement 2. Friction slows you down and causes heat.

Chapter 4 Review. Question What is the SI unit of force?

Problems – 1 A ball of mass ____ grams is tossed straight up in the air. Assuming air resistance can be ignored, draw an FBD for the ball on its way up.

-A force that opposes motion -Acts parallel to the surfaces in contact.

Frictional Force A force that opposes motion Acts parallel to the

Sliding Friction A force that opposes motion Acts parallel to the

Friction & Inclined Planes

Friction Coefficient.

Newton’s Laws - continued

Static and Kinetic Frictional Forces Read 5.1 OpenStax

The force of Friction Chapter 4.4.

Module 4, Recitation 3 Concept Problems, Friction.

Free Body diagrams and problem solving

Refresher: *Acceleration is only caused by an unbalanced net force acting on an object. F = ma F = F1 + F2 + … *The weight of an object is referred to.

More Fun with Newton’s Laws

Newton’s Laws Acceleration

Free Body diagrams and problem solving

Free Body diagrams and problem solving

Aim: How do we explain the force of friction?

Ch. 10 slides WorkEnergy.ppt.

Thought Problem 1: You are traveling along a freeway at 65 mi/h. Your car has kinetic energy. You now brake to a stop because of congestion in traffic.

Contact Friction Forces:

Newton’s Laws - continued

Forces of Friction When an object is in motion on a surface or through a viscous medium, there will be a resistance to the motion This is due to the interactions.

Newton’s Laws - continued

Aim: How do we explain motion along an inclined plane?

Work and Power.

Friction & Inclined Planes

Involving Friction and the coefficients of friction

Aim: How do we explain the force of friction?

Dynamics III Friction and Inclines.

Involving Friction and the coefficients of friction

Newton’s Laws - continued

How does an inclined plane make work easier How does an inclined plane make work easier? How does it change the force that is applied to the inclined.

Applying Newton’s Laws

Newton’s Laws - continued

Contact Friction Forces:

Presentation transcript:

Friction

Frictional Forces Friction has its basis in surfaces that are not completely smooth:

Static Friction

Static Friction Static friction keeps an object from starting to move when a force is applied. Static frictional force has a maximum value, but may take on any value from zero to the maximum,

Static Frictional Forces (6-2) where (6-3)

Kinetic Friction Fpush > fk = mkn

Kinetic Friction Kinetic friction: the friction experienced by surfaces sliding against one another Kinetic frictional force depends on the normal force: (6-1) Constant is called the coefficient of kinetic friction.

Kinetic Friction and Speed kinetic friction is independent of relative speed of the surfaces, and of their area of contact.

Coefficients of Friction fs £ msFn fs max = msFn fk = mkFn Typically, ms>mk

Horizontal Retarding Friction A cruise-ship passenger uses a shuffleboard cue to push a shuffleboard disk of mass 0.40 kg horizontally along the deck, so that the disk leaves the cue at a speed of 8.5 m/s. The disk then slides a distance of 8.0 m. What is the coefficient of kinetic friction between the disk and deck? m = 0.40 kg v0x = 8.5 m/s x0 = 0 x = 8.0 m vx = 0

Friction ACT1 You push two identical bricks across a tabletop with constant speed v. Which Case, as shown above, requires more force Fn? a. F1>F2 b. F1=F2 c. F1<F2 d. Need to know brick areas to answer

Inclined Plane Friction Suppose a 20 kg object is sliding down a 50o inclined plane. If µk = 0.4 between the plane surface and the object, what is the object’s acceleration down the plane? How long will it take the object to slide 5.0 m if it starts from rest?. k F

Friction with  Component of Tension Two children sitting on a sled at rest in the snow ask you to pull them. You oblige by pulling on the sled’s rope, which makes an angle of 40° with the horizontal. The children have a combined mass of 45 kg, and the sled has a mass of 5.0 kg. The coefficient of kinetic friction is mk=0.15. Find the acceleration of the sled and children if the rope tension is 140 N.

Antilock Brakes

Antilock Brakes A car is traveling at 30 m/s along a horizontal road. The coefficients of friction are ms=0.50 and mk=0.40. (a) What is the braking distance Dxa with antilock brakes? (b) What is the braking distance Dxb if the brakes lock?