Chapter 5 Using Newton’s Laws with Friction, Circular Motion and Drag Forces

Introduction: Our approach Additions to our understanding on each side of ∑F = ma On the ∑F side:Friction – static and kinetic On the ma side: Circular motion – uniform motion – highway curves, banked and not – non-uniform motion More on the ∑F side: Drag force – terminal velocity

Friction Kinds (“rolling” later) – kinetic (sliding) – static Complex phenomena Example EXERCISE EXERCISE Problem solving using Newton’s Laws – location of additions to problem solving (see)see – framing the problem (esp. with static friction)

Uniform Circular Motion Acceleration – direction EXERCISE – representation (a R and a tan ) – uniform (=?) – a R = v 2 /R – a tan = 0 Exercises, examples Problem solving using Newton’s Laws – location of additions to problem solving (see)see

Highway Curves; Banked & Not Relation to both sides of Newton’s 2 nd Law When is there sliding on unbanked curves? What is the friction force on vehicles going on banked curves? Resource: battista/banked_curve/banked_curve.html battista/banked_curve/banked_curve.html

Non-uniform Circular Motion Components of acceleration – meaning – total acceleration (?) – magnitude of acceleration (?) Relation to Cartesian coordinate representation

Drag Force At “low” and “high” speeds; velocity dependence (?) Example, low speeds (e.g. boat in water) Terminal velocity – key? (a = 0) Example: In slow case, derive the expression for the terminal velocity? – Graph (roughly) the x,v,a motion graphs (?) Modeling, if time available

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friction exercise in groups, get whiteboards, pens, erasers Question: At what angle does a wood block slide down a wood incline? (See table 5-1.) – include other variables as needed Question: At this angle, describe the motion of the wood block down the wood incline? back

Using Newton’s Laws The Physical situation Choose/identify objects and forces Create simple FBDs Choose inertial coordinate systems Implement Newton’s Laws Mathematical representation Solution Problem back

Using Newton’s Laws The Physical situation Choose/identify objects and forces Create simple FBDs Choose inertial coordinate systems Implement Newton’s Laws Mathematical representation Solution Problem back