Ch4_AronskyA

= = toc

= = =**Homework** =

Lesson 1 (a-d)
11/14

//1. What is Newton's First Law of Motion?// //2. What are the applications of Newton's First Law to real life?// //3. What are inertia and mass?// //4. Who is Galileo and what is his relationship with inertia?// //5. Why don't forces keep object moving?// //6. How is mass a measure of inertia?// //7. What is meant by the state of motion?// //8. What are balanced and unbalanced forces?//
 * law of inertia
 * states "an object at rest stays at rest and an object in motion stays in motion with the same speed and in the same direction and in the same direction unless acted upon by an unbalanced force"
 * objects keep on doing what they're doing unless there is an **unbalanced** force
 * when you break in a car, coffee continues at the same speed and will go into the windshield when the car slows down, even though the car is stopped
 * <span style="font-family: Tahoma,Geneva,sans-serif;">blood rushes from head to feet in an elevator
 * <span style="font-family: Tahoma,Geneva,sans-serif;">headrests are placed in cars to prevent whiplash injuries during rear-end collisions
 * <span style="font-family: Tahoma,Geneva,sans-serif;">inertia: the resistance an object has to a change in its state of motion
 * <span style="font-family: Tahoma,Geneva,sans-serif;">mass: quantity that is solely dependent on the inertia of an object. A more massive object has a great tendency to resist change in its state of motion
 * <span style="font-family: Tahoma,Geneva,sans-serif;">first scientist to come up with the idea of inertia
 * <span style="font-family: Tahoma,Geneva,sans-serif;">claimed that thinking objects had a tendency to stop was not due to inertia but was because of friction
 * <span style="font-family: Tahoma,Geneva,sans-serif;">reasoned that if a ball went down a plane and up another, regardless of angle, it would reach almost the same height
 * <span style="font-family: Tahoma,Geneva,sans-serif;">the difference between final and initial heights are due to inertia
 * <span style="font-family: Tahoma,Geneva,sans-serif;">presence of a force, friction, eventually stops the motion of an object across a surface; force brings objects to rest
 * <span style="font-family: Tahoma,Geneva,sans-serif;">The more inertia that an object has, the more mass that it has; more massive object has a greater tendency to resist changes in its state of motion.
 * <span style="font-family: Tahoma,Geneva,sans-serif;">the state of motion of an object is defined by its velocity
 * <span style="font-family: Tahoma,Geneva,sans-serif;">an object at a rest with a velocity of 0 will remain that way unless acted on by an unbalanced force
 * <span style="font-family: Tahoma,Geneva,sans-serif;">inertia can be redefined as the tendency of an object to resist changes in its velocity
 * <span style="font-family: Tahoma,Geneva,sans-serif;">when two forces are of equal magnitude and in opposite directions, they balance each other - the object is at equilibrium
 * <span style="font-family: Tahoma,Geneva,sans-serif;">if forces are not the same magnitude, or not in the opposite directions, then they are unbalanced
 * <span style="font-family: Tahoma,Geneva,sans-serif;">unbalanced forces cause acceleration

<span style="font-family: Tahoma,Geneva,sans-serif;">Lesson 2 (a-d)
<span style="font-family: Tahoma,Geneva,sans-serif;">11/16

<span style="font-family: Tahoma,Geneva,sans-serif;">__**A:**__ <span style="font-family: Tahoma,Geneva,sans-serif;">//What is a force?// <span style="font-family: Tahoma,Geneva,sans-serif;">//What are contact forces? What are some examples?// <span style="font-family: Tahoma,Geneva,sans-serif;">//What are action-at-a-distance forces? What are some examples?// <span style="font-family: Tahoma,Geneva,sans-serif;">//Describe Newtons.// <span style="font-family: Tahoma,Geneva,sans-serif;">__**B:**__ <span style="font-family: Tahoma,Geneva,sans-serif;">//Name and describe the different types of forces.// <span style="font-family: Tahoma,Geneva,sans-serif;">//Why are mass and weight confused?// <span style="font-family: Tahoma,Geneva,sans-serif;">//What's the difference between sliding and static friction?// __<span style="font-family: Tahoma,Geneva,sans-serif;">**C:** __ <span style="font-family: Tahoma,Geneva,sans-serif;">//What is a free-body diagram and how do you draw one?// <span style="font-family: Tahoma,Geneva,sans-serif;">
 * <span style="font-family: Tahoma,Geneva,sans-serif;">forces are pushes or pulls upon objects which result from the object's interaction with another
 * <span style="font-family: Tahoma,Geneva,sans-serif;">forces only exist as a result of an interaction
 * <span style="font-family: Tahoma,Geneva,sans-serif;">contact forces result when two interacting objects are perceived to be physically contacting each other
 * <span style="font-family: Tahoma,Geneva,sans-serif;">examples: frictional, tensional, normal, air resistances, applied, and spring forces
 * <span style="font-family: Tahoma,Geneva,sans-serif;">forces that result even when two interacting objects aren't in physical contact with each other, yet still exert a push or pull despite their physical separation
 * <span style="font-family: Tahoma,Geneva,sans-serif;">examples: gravitational, electrical, and magnetic forces
 * <span style="font-family: Tahoma,Geneva,sans-serif;">ex: sun and planets have a gravitational pull on each other despite large separation
 * <span style="font-family: Tahoma,Geneva,sans-serif;">ex: two magnets can exert a magnetic pull on each other when separated
 * <span style="font-family: Tahoma,Geneva,sans-serif;">they are units that forces are measured in
 * <span style="font-family: Tahoma,Geneva,sans-serif;">abbreviated as N and equal to 1 kg*m/s 2
 * <span style="font-family: Tahoma,Geneva,sans-serif; vertical-align: sub;">not a full description of a force because it don't show direction, which is required to explain a force (needs magnitude and direction)
 * <span style="font-family: Tahoma,Geneva,sans-serif;">**Applied Force**: force that is applied to an object by a person or another object
 * <span style="font-family: Tahoma,Geneva,sans-serif;">**Gravity Force/Weight**: force that the earth, moon, or other large objects attracts other objects towards itself; this is the weight of an object, on earth it is directed downwards towards the center of the earth; force of gravity is always equal to the weight of the object (Fgrav= mXg)
 * <span style="font-family: Tahoma,Geneva,sans-serif;">**Normal Force:** the support force exerted upon an object that is in contact with another stable object
 * <span style="font-family: Tahoma,Geneva,sans-serif;">book resting upon a surface, then the surface is exerting an upward force upon the book in order to support the weight of the book
 * <span style="font-family: Tahoma,Geneva,sans-serif;">**Friction Force:** the force exerted by a surface as an object moves across it or makes an effort to move across it; there are two types: sliding and static; friction force often opposes motion of the object; maximum amount of friction is (Ffrict = µ • Fnorm)**Air Resistance Force:** special type of frictional force that acts upon objects as they travel through air; usually opposes motion of an object
 * <span style="font-family: Tahoma,Geneva,sans-serif;">book slides across a desk, then desk exerts a friction force in the opposite direction of its motion
 * <span style="font-family: Tahoma,Geneva,sans-serif;">**Tension Force:** force that is transmitted through a strong, rope, cable, or wire when it is pulled tight by forces acting from opposite ends
 * <span style="font-family: Tahoma,Geneva,sans-serif;">**Spring Force:** exerted by a compressed or stretched string upon an object attached to it; an object that compresses or stretches a string is always acted upon by a force that restores the object to its rest or equilibrium position
 * <span style="font-family: Tahoma,Geneva,sans-serif;">**Spring Force:** exerted by a compressed or stretched string upon an object attached to it; an object that compresses or stretches a string is always acted upon by a force that restores the object to its rest or equilibrium position
 * <span style="font-family: Tahoma,Geneva,sans-serif;">mass refers to the amount of matter contained by the object
 * <span style="font-family: Tahoma,Geneva,sans-serif;">weight is the force of gravity acting upon the object
 * <span style="font-family: Tahoma,Geneva,sans-serif;">mass is measured in kilograms and will be the same no matter where in the universe the object is located while the weight of an object is measured in Newtons and will vary according to where in the universe it is
 * <span style="font-family: Tahoma,Geneva,sans-serif;">Sliding friction results when an object slides across a surface
 * <span style="font-family: Tahoma,Geneva,sans-serif; line-height: 22px;">**Sliding Ffrict = μ • Fnorm**
 * <span style="font-family: Tahoma,Geneva,sans-serif;">Static friction results when surfaces of two objects are at rest relative to one another and a force exists on one of the objects to set it into motion relative to the other object
 * <span style="font-family: Tahoma,Geneva,sans-serif;">**Ffrict-static ≤ μfrict-static• Fnorm**
 * <span style="font-family: Tahoma,Geneva,sans-serif;">FBD are used to show the relative magnitude and direction of all forces acting upon an object in a given situation
 * <span style="font-family: Tahoma,Geneva,sans-serif;">the size of the arrows reflects the magnitude of the force
 * <span style="font-family: Tahoma,Geneva,sans-serif;">the direction of the arrow shows the direction that the force is acting
 * <span style="font-family: Tahoma,Geneva,sans-serif;">each arrow is labeled to indicate the type of force it is
 * <span style="font-family: Tahoma,Geneva,sans-serif;">usually the object is represented by a box and arrows are drawn from the center in the outward direction

__<span style="font-family: Tahoma,Geneva,sans-serif;">**D:** __ <span style="font-family: Tahoma,Geneva,sans-serif;">//How do you determine the net force?//
 * <span style="font-family: Tahoma,Geneva,sans-serif;">the net force is the vector sum of all the force that act upon an object
 * <span style="font-family: Tahoma,Geneva,sans-serif;">it is the sum of all the forces, taking into account the fact that a force is a vector and two forces of equal magnitude and opposite direction will cancel each other out
 * <span style="font-family: Tahoma,Geneva,sans-serif;">a net force causes acceleration



<span style="font-family: Tahoma,Geneva,sans-serif; font-size: 1.3em;">Lesson 3 (a-b)
<span style="font-family: Tahoma,Geneva,sans-serif;">11/17

__<span style="font-family: Tahoma,Geneva,sans-serif;">**A:** __ <span style="font-family: Tahoma,Geneva,sans-serif;">//What is Newton's Second Law?// __<span style="font-family: Tahoma,Geneva,sans-serif;">**B:** __ <span style="font-family: Tahoma,Geneva,sans-serif;">//What's the big misconception with Newton's law?// <span style="font-family: Tahoma,Geneva,sans-serif;"> =<span style="font-family: Tahoma,Geneva,sans-serif;">Vectors: Lesson 3 Summary = <span style="font-family: Tahoma,Geneva,sans-serif;">
 * <span style="font-family: Tahoma,Geneva,sans-serif;">pertains to the behavior of objects for which all existing forces are not balanced
 * <span style="font-family: Tahoma,Geneva,sans-serif;">acceleration of an object is dependent on the net force acting upon the object and the mass of the object
 * <span style="font-family: Tahoma,Geneva,sans-serif;">force acting upon an object is increased, so is acceleration
 * <span style="font-family: Tahoma,Geneva,sans-serif;">mass of object is increased, acceleration of object is decreased
 * <span style="font-family: Tahoma,Geneva,sans-serif;">"acceleration of an object as produced by a net force is directly proportional to the magnitude of the net force, in the same direction as the net force, and inversely proportional to the mass of the object"
 * <span style="font-family: Tahoma,Geneva,sans-serif;">a = Fnet / m
 * <span style="font-family: Tahoma,Geneva,sans-serif;">acceleration is directly proportional to net force and in the same direction as net force
 * <span style="font-family: Tahoma,Geneva,sans-serif;">it is hard to understand the meaning and believe the implications of the laws
 * <span style="font-family: Tahoma,Geneva,sans-serif;">we can overcome misconceptions by self-reflection, critical thinking, and evaluation
 * <span style="font-family: Tahoma,Geneva,sans-serif;">most common misconception is that sustaining motion requires a continued force
 * <span style="font-family: Tahoma,Geneva,sans-serif;">Newton's law states that a net force (unbalanced force) causes acceleration; acceleration is in the same direction as net force
 * <span style="font-family: Tahoma,Geneva,sans-serif;">truth is that a force is NOT needed for an object to stay in motion, but the presence of a force like friction will stop motion
 * <span style="font-family: Tahoma,Geneva,sans-serif;">//Addition of Forces//
 * <span style="font-family: Tahoma,Geneva,sans-serif;">one method of addition of vectors: head-to-tail method
 * <span style="font-family: Tahoma,Geneva,sans-serif;">the purpose of adding force vectors is to determine the net force acting upon an object
 * <span style="font-family: Tahoma,Geneva,sans-serif;">when an object is at equilibrium, the net force is zero newtons
 * <span style="font-family: Tahoma,Geneva,sans-serif;">whenever objects are accelerating, the forces will not balance and the net force will NOT be zero
 * <span style="font-family: Tahoma,Geneva,sans-serif;">//Resolution of Forces//
 * <span style="font-family: Tahoma,Geneva,sans-serif;">single forces can be resolved into two components: one directed upwards and the other directed rightwards
 * <span style="font-family: Tahoma,Geneva,sans-serif;">each component describes the influence of that force in the given direction
 * <span style="font-family: Tahoma,Geneva,sans-serif;">the vertical component describes the upward influence and the horizontal force describes the rightward influence
 * <span style="font-family: Tahoma,Geneva,sans-serif;">use trigonometry to to deteremine the components
 * <span style="font-family: Tahoma,Geneva,sans-serif;">//Equilibrium and Statics//
 * <span style="font-family: Tahoma,Geneva,sans-serif;">when all the forces that act upon an object are balanced, then the object is said to be in a state of equilibrium --> the forces are balanced.
 * <span style="font-family: Tahoma,Geneva,sans-serif;">this does not necessarily mean that all forces are equal to each other
 * <span style="font-family: Tahoma,Geneva,sans-serif;">when forces are balanced, the net force is zero and acceleration is 0 m/s/s.
 * <span style="font-family: Tahoma,Geneva,sans-serif;">an object at equilibrium is either at rest at staying at rest or in motion and continuing in motion at the same speed and direction
 * <span style="font-family: Tahoma,Geneva,sans-serif;">static means stationary or at rest so if an object is in a state of equilbirum and at rest, it is at static equilibrium
 * <span style="font-family: Tahoma,Geneva,sans-serif;">//Net Force Problems Revisted//
 * <span style="font-family: Tahoma,Geneva,sans-serif;">forces can be broken down into two components
 * <span style="font-family: Tahoma,Geneva,sans-serif;">these two components can be considered to replace the applied force at an angle
 * <span style="font-family: Tahoma,Geneva,sans-serif;">//Inclined Planes//
 * <span style="font-family: Tahoma,Geneva,sans-serif;">an object placed on a tilted surface will often slide down the surface
 * <span style="font-family: Tahoma,Geneva,sans-serif;">the rate at which it slides down is dependent on how tilted the surface is
 * <span style="font-family: Tahoma,Geneva,sans-serif;">the greater the tilt --> the faster object goes
 * <span style="font-family: Tahoma,Geneva,sans-serif;">tilted surface --> inclined plane
 * <span style="font-family: Tahoma,Geneva,sans-serif;">objects accelerate down inclined planes because of an unbalanced force
 * <span style="font-family: Tahoma,Geneva,sans-serif;">the force of gravity acts in a downward motion; yet the normal force acts in a direction perpendicular to the surface
 * <span style="font-family: Tahoma,Geneva,sans-serif;">//Two Body Problems//
 * <span style="font-family: Tahoma,Geneva,sans-serif;">two body problems involve solving for the acceleration of the objects and the force that is acting between the objects
 * <span style="font-family: Tahoma,Geneva,sans-serif;">one strategy of solving is to determine the acceleration combined with an individual object analysis to determine the force transmitted between the objects
 * <span style="font-family: Tahoma,Geneva,sans-serif;">the second strategy is to use the two individual objects in order to develop a system of two equations for solving for the two unknown quantitie s
 * <span style="font-family: Tahoma,Geneva,sans-serif;">the second strategy is to use the two individual objects in order to develop a system of two equations for solving for the two unknown quantitie s