Ch4_GrunfeldM

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 * Chapter 4 **


 * Newton's First Law of Motion **

=**Lesson 1a: Newton's First Law **=


 * **What is Newton's first law of motion?**
 * Also referred to as the law of inertia
 * **Newton's first law of motion** = an object at rest stays at rest and an object in motion stays in motion with the same speed and in the same direction unless acted upon by an unbalanced force
 * **How can you apply Newton's first law of motion to everyday life? **
 * Blood rushes from your head to your feet while quickly stopping when riding on a descending elevator
 * To dislodge ketchup from the bottom of a ketchup bottle, it is often turned upside down and thrusted downward at high speeds and then abruptly halted
 * While riding a skateboard (or wagon or bicycle), you fly forward off the board when hitting a curb or rock or other object that abruptly halts the motion of the skateboard

=Lesson 1b: Inertia and Mass =


 * **What is inertia? **
 * **Inertia** = the tendency of an object to resist changes in its state of motion
 * **<span style="font-family: 'Comic Sans MS',cursive;">What does mass have to do with Newton's first law of motion? **
 * <span style="font-family: 'Comic Sans MS',cursive;">An object's inertia varies with its mass
 * <span style="font-family: 'Comic Sans MS',cursive;">The more inertia an object has, the more mass it has
 * **<span style="font-family: 'Comic Sans MS',cursive;">How did Galileo contribute to Newton's law of inertia? **
 * <span style="font-family: 'Comic Sans MS',cursive;">Galileo developed the concept of inertia
 * <span style="font-family: 'Comic Sans MS',cursive;">Reasoned that moving objects eventually stop because of a force called friction
 * **<span style="font-family: 'Comic Sans MS',cursive;">If forces don't keep objects moving, what does? **
 * <span style="font-family: 'Comic Sans MS',cursive;">The absence of a force keeps objects moving; forces actually put moving objects to rest

=<span style="font-family: 'Comic Sans MS',cursive;">Lesson 1c: State of Motion =


 * **<span style="font-family: 'Comic Sans MS',cursive;">What is meant by the phrase "state of motion"? **
 * <span style="font-family: 'Comic Sans MS',cursive;">The <span style="color: #ff0000; font-family: 'Comic Sans MS',cursive;">**state of motion** of an object is defined by its velocity (speed with a direction)
 * <span style="font-family: 'Comic Sans MS',cursive;">Therefore, inertia = the tendency of an object to resist changes in its velocity
 * <span style="font-family: 'Comic Sans MS',cursive;">An object at rest has a velocity of 0 (not changing) and an object that is not changing its velocity is said to have an acceleration of 0 m/s2
 * <span style="font-family: 'Comic Sans MS',cursive;">Therefore, inertia = the tendency of an object to resist accelerations

=<span style="font-family: 'Comic Sans MS',cursive;">Lesson 1d: Balanced and Unbalanced Forces =


 * <span style="font-family: 'Comic Sans MS',cursive;">**What is the difference between a balanced and an unbalanced force?**
 * <span style="color: #ff0000; font-family: 'Comic Sans MS',cursive;">**Balanced Forces:**
 * <span style="font-family: 'Comic Sans MS',cursive;">**__Ex:__** a book at rest on a tabletop. 2 forces acting on the book: the Earth's gravitational pull (downward force) and the push of the table on the book (upward force)
 * <span style="font-family: 'Comic Sans MS',cursive;">The book is at equilibrium (no unbalanced forces)
 * <span style="color: #ff0000; font-family: 'Comic Sans MS',cursive;">**Unbalanced Forces:**
 * <span style="font-family: 'Comic Sans MS',cursive;">**__Ex:__** a book sliding from left to right across a tabletop. 3 forces: gravity (downward force), the push of the table on the book (upward force), and friction (leftward force) upon the book moving rightward
 * <span style="font-family: 'Comic Sans MS',cursive;">The book is changing its state of motion/accelerating



<span style="font-family: 'Comic Sans MS',cursive; font-size: 140%;">**Force and Its Representation**

=<span style="font-family: 'Comic Sans MS',cursive;">Lesson 2a: The Meaning of Force =


 * **<span style="font-family: 'Comic Sans MS',cursive;">What is the meaning of force? **
 * <span style="font-family: 'Comic Sans MS',cursive;">A **force** = a push or pull upon an object resulting from the object's //interaction// with another object
 * <span style="font-family: 'Comic Sans MS',cursive;">Vector quantity (has both magnitude and direction)
 * <span style="font-family: 'Comic Sans MS',cursive;">All forces (interactions) between objects can be placed into two broad categories:
 * <span style="font-family: 'Comic Sans MS',cursive;"> **Contact forces** = types of forces that result when two interacting objects are perceived to be physically contacting each other
 * <span style="font-family: 'Comic Sans MS',cursive;">__**Ex:**__ Frictional forces, tensional forces, normal forces, air resistance forces, and applied forces
 * <span style="font-family: 'Comic Sans MS',cursive;"> **Action-at-a-distance forces** = types of forces that result even when the two interacting objects are not in physical contact with each other, yet are able to exert a push or pull despite their physical separation
 * <span style="font-family: 'Comic Sans MS',cursive;">**__Ex:__** Gravitational forces, electric forces, magnetic forces

=<span style="font-family: 'Comic Sans MS',cursive;">Lesson 2b: Types of Forces =


 * <span style="font-family: 'Comic Sans MS',cursive;">**What are some of the different types of forces (in detail)?**
 * <span style="font-family: 'Comic Sans MS',cursive;">** Applied force (Fapp)** = a force that is applied to an object by a person or another object
 * <span style="font-family: 'Comic Sans MS',cursive;">** Gravity force/Weight (Fgrav)** = the force with the earth, moon, or other massively large object attracts another object toward itself (weight); directed "downward" toward the center of the earth [[image:Screen_shot_2011-11-15_at_6.03.53_PM.png]]
 * <span style="font-family: 'Comic Sans MS',cursive;">** Normal force (Fnorm)** = the support force exerted on an object that is in contact with another stable object
 * <span style="font-family: 'Comic Sans MS',cursive;">** Friction force (Ffrict)** = the force exerted by a surface as an object moves across it or makes an effort to move across it; the friction force often opposes the motion of an object; 2 types: sliding and static friction
 * <span style="font-family: 'Comic Sans MS',cursive;">** Air resistance force (Fair)** = a special type of frictional force that acts upon objects as they travel through air
 * <span style="font-family: 'Comic Sans MS',cursive;">** Tension force (Ftens)** = the force that is transmitted through a string, rope, cable, or wire when it is pulled tight by forces acting from opposite ends
 * <span style="font-family: 'Comic Sans MS',cursive;">** Spring force (Fspring)** = the force exerted by a compressed or stretched spring upon any object that is attached to it
 * <span style="font-family: 'Comic Sans MS',cursive;">**What is the confusion between mass and weight?**
 * <span style="font-family: 'Comic Sans MS',cursive;"> **Weight** = the force of gravity acting upon an object
 * <span style="font-family: 'Comic Sans MS',cursive;"> **Mass** = the amount of matter that is contained by an object
 * <span style="font-family: 'Comic Sans MS',cursive;">Weight will vary according to where in the universe the object is; mass will not

=<span style="font-family: 'Comic Sans MS',cursive;">Lesson 2c: Drawing Free-Body Diagrams =


 * **<span style="font-family: 'Comic Sans MS',cursive;">How do you draw a free-body diagram? **
 * <span style="font-family: 'Comic Sans MS',cursive;">A **free-body diagram** = a diagram used to show the relative magnitude and direction of all forces acting upon an object in a given situation
 * <span style="font-family: 'Comic Sans MS',cursive;">Size of the arrow reflects the magnitude of the force
 * <span style="font-family: 'Comic Sans MS',cursive;">Direction of the arrow shows the direction that the force is acting
 * <span style="font-family: 'Comic Sans MS',cursive;">Each force arrow in the diagram is labeled to indicate the exact type of force
 * <span style="font-family: 'Comic Sans MS',cursive;">Customary to represent the object by a box and to draw the force arrow from the center of the box outward in the direction that the force is acting

=<span style="font-family: 'Comic Sans MS',cursive;">Lesson 2d: Determining the Net Force =


 * **<span style="font-family: 'Comic Sans MS',cursive;">How do you determine the net force of an object? **
 * <span style="font-family: 'Comic Sans MS',cursive;">In all situations with an unbalanced force, there is a net force
 * <span style="font-family: 'Comic Sans MS',cursive;">A <span style="color: #ff0000; font-family: 'Comic Sans MS',cursive;">**net force** = the vector sum of all the forces that act upon an object




 * <span style="font-family: 'Comic Sans MS',cursive; font-size: 140%;">Newton's Second Law of Motion **

=<span style="font-family: 'Comic Sans MS',cursive;">Lesson 3a: Newton's Second Law =

<span style="font-family: 'Comic Sans MS',cursive;">__**or**__
 * <span style="font-family: 'Comic Sans MS',cursive;">**What is Newton's second law of motion?**
 * <span style="font-family: 'Comic Sans MS',cursive;">Pertains to the behavior of objects for which all existing forces are __not__ balanced
 * <span style="font-family: 'Comic Sans MS',cursive;"> **Newton's second law of motion** = the acceleration of an object is dependent upon two variables: the net force acting upon the object and the mass of the object; the acceleration of an object depends directly upon the net force acting upon it and inversely upon the mass

=<span style="font-family: 'Comic Sans MS',cursive;">Lesson 3b: The Big Misconception =


 * **<span style="font-family: 'Comic Sans MS',cursive;">What is the big misconception about Newton's laws? **
 * <span style="font-family: 'Comic Sans MS',cursive;">The most common misconception that dates back for ages is the idea that sustaining motion requires a continued force
 * <span style="font-family: 'Comic Sans MS',cursive;">A force is not needed to keep an object in motion; the force (friction) actually brings the object to rest
 * <span style="font-family: 'Comic Sans MS',cursive;">In the absence of a force of friction, an object would continue with the same speed in the same direction forever
 * <span style="font-family: 'Comic Sans MS',cursive;">Forces do not cause motion; forces cause accelerations

=<span style="font-family: 'Comic Sans MS',cursive;">Lesson 3c: Finding Acceleration =


 * <span style="font-family: 'Comic Sans MS',cursive;">**How do you find the acceleration in any given situation?**
 * <span style="font-family: 'Comic Sans MS',cursive;">The process of determining the acceleration of an object demands that the mass and the net force are known

=<span style="font-family: 'Comic Sans MS',cursive;">Lesson 3d: Finding Individual Forces =


 * **<span style="font-family: 'Comic Sans MS',cursive;">How do you find the individual forces in any given situation? **
 * <span style="font-family: 'Comic Sans MS',cursive;">The process of determining the value of the individual forces acting upon an object demands that mass and acceleration are known

=<span style="font-family: 'Comic Sans MS',cursive;">Lesson 3e: Free Fall and Air Resistance =


 * <span style="font-family: 'Comic Sans MS',cursive;">**Why do all objects fall at the same rate of acceleration regardless of their mass?**
 * <span style="font-family: 'Comic Sans MS',cursive;">Using the equation Fnet = ma, an object with a smaller mass requires a greater force to move it, and an object with a larger mass requires a lesser force
 * <span style="font-family: 'Comic Sans MS',cursive;">Thus, the proportion of F/m in both situations results in the same acceleration
 * <span style="font-family: 'Comic Sans MS',cursive;">**Why do objects that encounter air resistance ultimately reach a terminal velocity?**
 * <span style="font-family: 'Comic Sans MS',cursive;"> **Air resistance** = the result of collisions of an object's leading surface with air molecules
 * <span style="color: #ff0000; font-family: 'Comic Sans MS',cursive;">**Terminal velocity** = <span style="font-family: 'Comic Sans MS',cursive;">the termination of the change in velocity as a result of the balance of forces (net force 0 N; object stops accelerating)
 * <span style="font-family: 'Comic Sans MS',cursive;">Eventually, the force of air resistance becomes large enough to balance the force of gravity, resulting in terminal velocity
 * <span style="font-family: 'Comic Sans MS',cursive;">**In situations in which there is air resistance, why do more massive objects fall faster than less massive objects?**
 * <span style="font-family: 'Comic Sans MS',cursive;">A falling object will continue to accelerate to higher speeds until it encounters an amount of air resistance that is equal to its weight
 * <span style="font-family: 'Comic Sans MS',cursive;">Objects that weigh more (and experience a greater force of gravity) will accelerate to higher speeds before reaching a terminal velocity
 * <span style="font-family: 'Comic Sans MS',cursive;">Thus, more massive objects fall faster than less massive objects because they are acted upon by a larger force of gravity

=<span style="font-family: 'Comic Sans MS',cursive;">Lesson 3f: Double Trouble (a.k.a., Two Body Problems) =


 * <span style="font-family: 'Comic Sans MS',cursive;">**How do you solve two-body problems?**
 * <span style="font-family: 'Comic Sans MS',cursive;"> **Two-body problems** = problems that are characterized by a set of two unknown quantities
 * <span style="font-family: 'Comic Sans MS',cursive;">Two basic approaches:
 * <span style="font-family: 'Comic Sans MS',cursive;">1. Combination of a system analysis and an individual body analysis
 * <span style="color: #ff0000; font-family: 'Comic Sans MS',cursive;">**System Analysis:**
 * <span style="font-family: 'Comic Sans MS',cursive;">The two objects are considered to be a single object moving (or accelerating) together as a whole
 * <span style="font-family: 'Comic Sans MS',cursive;">The mass of the system is the sum of the mass of the two individual objects
 * <span style="font-family: 'Comic Sans MS',cursive;">Usually performed to determine the acceleration of the system
 * <span style="color: #ff0000; font-family: 'Comic Sans MS',cursive;">**Individual Object Analysis:**
 * <span style="font-family: 'Comic Sans MS',cursive;">Either one of the two objects is isolated and considered as a separate, independent object
 * <span style="font-family: 'Comic Sans MS',cursive;">A free-body diagram is constructed and the individual forces acting upon the object are identified and calculated
 * <span style="font-family: 'Comic Sans MS',cursive;">Usually performed in order to determine the value of any force which acts between the two objects
 * <span style="font-family: 'Comic Sans MS',cursive;">2. Two separate individual object analyses
 * <span style="font-family: 'Comic Sans MS',cursive;">Free-body diagrams are constructed independently for each object and Newton's second law is used to relate the individual force values to mass and acceleration
 * <span style="font-family: 'Comic Sans MS',cursive;">Each individual object analysis generates an equation with a different unknown for each
 * <span style="font-family: 'Comic Sans MS',cursive;">The system of equations is solved in order to determine the unknown values