Ch4_WeissB

=__Chapter 4__= toc

**Summarization (Version 4) of Newton's Laws Lesson 1**
Date: 11/14/11

1. How is motion explained through Newton's First Law? Newton shows with this law that objects will "keep on doing what they are doing" (not moving at all or moving at a constant rate) as long as an unbalanced force does not act on it. Otherwise, the object will move at constant speed in a straight line if it was in motion to begin with.

2. How is the First Law relevant in everyday life? The First Law is true of many things in everyday life, from the movement of liquids, etc. It is also the reason for seat belts; when a car stops, the passenger will keep moving unless stopped by something.

3. What was Newton's idea of inertia? Newton stated that inertia is a property that measures an object's resistance to change in its state of motion.

4. How did Galileo conceive the concept of inertia? Galileo created the concept of inertia from experiments that demonstrated a moving object that started off at a certain height would move until it reached that height again.

5. How did Newton develop and expand upon Galileo's concept of inertia? Though Galileo believed that inertia was due to the absence of friction, Newton expanded the concept of inertia to show that it was due to the presence of friction.

6. What is mass' relation to inertia? When an object has greater inertia, it has greater mass. When an object has less inertia, it has less mass.
 * Important: mass is not the same as weight; weight is a force, the pull of gravity on a mass; the standard measurement for mass in this scenario is kg, while the measure of weight is N; weight= m x g**

7. What is meant by an object's state of motion? State of motion is defined by an object's velocity, the speed with a direction.

8. What did Newton mean by "unbalanced force" in his First Law? A force that is not counteracted by another force. When forces counteract each other, there is equilibrium.
 * Two types of equilibrium: static (at rest, no motion) and dynamic (constant speed); when an unbalanced force acts on an object, it will accelerate in the direction of the unbalanced force; net force is the addition of all the forces.**

Summarization (Version 4) of Newton's Laws Lesson 2
1. What is the meaning of force? A force is a push or pull upon an object resulting from that object's interaction with another object.

2. What are the different types of forces? Forces can be characterized as either contact forces (which result when the two objects are perceived to be physically contacting each other) and action-at-a-distance forces (which result when the objects do not have physical contact, but still exert a push or pull). Contact forces can include tension, friction, and normal forces, while action-at-a-distance forces include gravitational force.

3. How are mass and weight different? Mass refers to the amount of matter contained by an object, while weight is the measure of gravitational pull on that matter.

4. What is the difference between sliding and static friction? Sliding friction results when one object slides across another object and the object on which the first is sliding offers resistance against the sliding. Static friction occurs when the surfaces of two objects are at rest and friction is formed in an attempt to set one of the objects into motion.

5. What is the purpose of a free-body diagram in physics and how does one draw it? Free-body diagrams are diagrams used to show the relative magnitude and direction of all forces acting upon an object in a given situation. These diagrams are drawn by utilizing traditional vector diagrams and applying them to a shape which symbolizes the object upon which the forces are acting upon.

6. What is the relevance of net force and how does one calculate it? Net force is the vector sum of all forces that act upon an object. One calculates net force as they would with any other kind of vector.

Summarization (Version 4) of Newton's Laws Lesson 3a-b
1. What is Newton's second law and how does it explain motion? Newton's second law describes the motion of objects that are accelerating. Through the equation **net force= mass x acceleration**, acceleration is shown to be directly proportional to the net force that is causing the object to accelerate and inversely proportional to the mass of the object that is accelerating.

2. What is the "big misconception" of Newton's Laws and how does one overcome it? The big misconception regarding Newton's Laws is that objects really do require forces to stay in motion

Summarization (Version 4) of Newton's Laws Lesson 3c-f
1. How does one find acceleration when its mass and the sum of its individual forces are know? One finds acceleration through the use of the equation: a= net force/mass, a variation of the Second Law Equation.

2. How does one find the magnitude of individual forces? One can find the magnitude of individual equations through the Second Law Equation: net force= mass x acceleration (when the values of mass and acceleration are known). Once the total net force is found, one can either apply formulas to find specific forces (like weight, which is m x g or friction, which is μ x normal force) or use algebra for forces that cannot be found through a formula.

3. What is free-fall motion and why is it so special? Free-fall motion is motion in which the only force on the moving object is gravity. This kind of motion is very unique because all objects moving at free-fall will accelerate at the exact same rate (9.8 m/s2).

4. What is air resistance? Air resistance is formed from the collisions between a falling object's leading surface and the molecules of the air. Basically, it is the friction due to the object moving against the air molecules.

5. Why does air resistance force a falling object to reach a terminal velocity? Air resistance causes a falling object to reach a terminal velocity because as the falling object accelerates, the air resistance becomes greater and eventually becomes large enough to balance the pull of the object's weight. From this point on, there is no more acceleration and the object cannot increase its velocity.

6. How does one analyze two objects that are connected to each other and their forces? One would do this much like the way a single object would be analyzed, through free body diagrams and Newton's Laws. More specifically, one can chart out free body diagrams by either considering the objects to be separate or part of one whole system.