Ch4_WeinfeldM

= toc Chapter 4=

11/14 Newton's Laws Lesson 1 (a-d) Method 4

 * a. Newton's First Law**
 * What is 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.
 * Objects are going to keep doing whatever they are doing; they will only change if acted upon
 * "The lazy law"
 * Object in motion moves in straight line at constant speed until acted on
 * How can motion be explained?
 * Newton's laws can be used to explain why objects move the ways they do.


 * b. Inertia and Mass**
 * What are inertia and mass?
 * Inertia is the resistance an object has to a change in its state of motion.
 * Inertia is a property of matter that measures how difficult it is to change an object's motion. This is mass.
 * Mass is a quantity that is dependent on just the inertia of an object.
 * The more inertia an object has, the more mass it has.
 * Measure inertia with mass in kg


 * c. State of Motion**
 * What is an object's state of motion and what is it defined by?
 * State of motion is defined by the object's velocity - the speed with direction.
 * An object does not change its state of motion unless acted on by an unbalanced force.

//** Review: talked to parents**//
 * d. Balanced and Unbalanced Forces**
 * What is the difference between a balanced and unbalanced force?
 * When two forces are of equal magnitude and in opposite directions, they balance each other so the force is balanced.
 * balanced forces are at equilibrium - either static equilibrium (at rest) or dynamic equilibrium (constant speed)
 * When there is no force present to balance another, there is an unbalanced force. Unbalanced forces cause accelerations.

November 15 Notes
Newton's First Law: no change in motion unless an unbalanced force acts on the object ... otherwise it moves at constant speed in a straight line (Galileo came up with this idea)

Inertia is a property of matter that measures how difficult it is to change an object's motion.

Mass tells you how much inertia something has.

Weight is a force, pull of gravity on mass.

Mass is measured in kg and weight is measured in N

W = mg where g = 9.8 m/s/s

Newton's Second Law: when an unbalanced force acts on an object, it will accelerate in the direction of the unbalanced force.
 * if N > w, accelerate upwards/increasing speed up or slow down/decrease speed down with acceleration up

November 15 Newton's Laws Lesson 2 (a-d) Method 4
//**Review: talked to parents**//
 * a. The Meaning of Force**
 * What is the meaning of force?
 * A force is a push or pull upon an object resulting from the object's interaction with another object.
 * When there is an interaction between two objects, there is a force on each of the objects.
 * The forces no longer exist when the interaction stop.s
 * Forces exist as a result of an interaction
 * b. Types of Forces**
 * What are different types of forces?
 * Forces can result from contact or non-contact between two interacting objects.
 * Contact forces: frictional force, tension force, normal force, air resistance force, applied force, or spring force.
 * Action-at-a-distance forces: gravitational force, electrical force, magnetic force
 * An applied force is a force that is applied to an object by a person or another object
 * Gravity force is the weight of an object
 * A normal force is the support force extended upon an object that is in contact with another stable object.
 * A friction force is the force exerted by a surface as an object moves across it or makes an effort to move across it
 * An air resistance force is a special type of frictional force that acts upon objects as they travel through the air.
 * A tension force is the force that is transmitted through a string, rope, cable, or wire when it is pulled tight by forces acting from opposite ends.
 * A spring force is the force exerted by a compressed or stressed spring upon any object that is attached to it.
 * c. Drawing Free-Body Diagrams**
 * What is a free body diagram and what is their purpose?
 * Free-body diagrams are diagrams used to show the relative magnitude and direction of all forces acting upon an object in a given situation.
 * d. Determining the Net Force**
 * What is a net force and how is it determined?
 * The net force is the vector sum of all the forces that act upon an object
 * To find the net force, apply the the rules for summing vectors

11/17 Newton's Laws Lesson 3 (a-b) Method 4

 * a. Newton's Second Law**
 * What is Newton's second law and what does it pertain to?
 * Newton's second law of motion predicts the behavior of objects for which all existing forces are balanced.
 * Newton's second law pertains to the behavior of objects for which all existing forces are not balanced.
 * Newton's second law gives us the equation f=ma
 * b. The Big Misconception**
 * What is the big misconception in terms of Newton's laws of motion?
 * The problem is that most people just memorize the first law and use the second law to solve equations instead of really gaining the ability to understand their meaning and believe their implications.
 * The most common misconception is the idea that sustaining motion requires a continued force.
 * Newton's laws explain that a net force (an unbalanced force) causes an acceleration; the acceleration is in the same direction as the net force

12/6 Summarize Lesson 3

 * Addition of Forces
 * one method of addition of vectors is the head-to-tail method
 * the purpose of adding force vectors is to determine the net force acting upon an object
 * when an object is at equilibrium, the net force is 0N
 * whenever objects are accelerating, the forces will not balance and the net force will not be zero
 * Resolution of Forces
 * single forces can be resolved into two components - one directed upwards and the other directed righwards
 * each component describes the influence of that force in the given direction
 * the veritcal component describes the upward influence and the horizontal force describes the rightward influence
 * to deteremine the components, you use trigonometry
 * Equilibrium and Statics
 * 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.
 * this does not necessarily mean that all forces are equal to each other
 * when forces are balanced, the net force is zero and acceleration is 0 m/s/s.
 * 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
 * static means staionary or at rest so if an object is in a state of equilbirum and at rest, it is at static equilibrium
 * Net Force Problems Revisted
 * forces can be broken down into two components
 * these two components can be considered to replace the applied force at an angle
 * Inclined Planes
 * an object placed on a tilted surface will often slide down the surface
 * the rate at which it slides down is dependent on how tilted the surface is
 * the greater the tilt, the faster object goes
 * tilted surface = inclined plane
 * objects accelerate down inclined plances becuase of an ubalancedd force
 * the force of gravity acts in a downward motion; yet the normal force acts in a direction perpendicular to the surface
 * Double Trouble in 2 Dimensions (aka Two Body Problems)
 * two body problems involve solving for the acceleration of the objects and the force that is acting between the objects
 * one strategy of solving is to determine the acceleration combined with an individaul object analysis to determine the force transmitted between the objects
 * 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 quantities