Ch4_Doomank

= =

Honors Physics Rocks Wiki toc

= Homework 10/12/11 =
 * Newton's Laws Lesson 1**

**Parts a-d** 1. What is Newton's first law of motion? 2. What is inertia? 3. How are inertia and mass related? 3. How do we define a "state of motion"? 4. How do balanced and unbalanced forces affect an object and its motion?
 * Questions:**
 * 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 tend to "keep on doing what they're doing"
 * Example of real-life application: 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.
 * Inertia: the resistance an object has to a change in its [|state of motion]
 * Mass is that quantity that is __solely__ dependent upon the inertia of an object.
 * The more inertia that an object has, the more mass that it has.
 * Which means that a more massive object has a greater tendency to resist changes in its state of motion.
 * state of motion of an object is defined by its [|velocity] - the speed with a direction.
 * This means that inertia could be redefined as follows: **Inertia: tendency of an object to resist changes in its velocity**
 * Inertia could also be redefined as **Inertia: tendency of an object to resist accelerations**
 * When all the forces acting upon an object balance each other, the object will be at equilibrium
 * Newton's first law says "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."
 * This means that unbalanced forces //change// the motion of the object

= Homework 11/16/11 = Lesson 2

**Parts a-d**

Questions: 1. How is force defined? What is force? 2. What are the different kinds of forces? Under what circumstances are they present? 3. What is Net Force? How is it determined?
 * push or pull upon an object resulting from the object's //interaction// with another object; whenever there is an //interaction// between two objects, there is a force upon each of the objects
 * when the //interaction// stops, the two objects no longer experience the force.
 * Forces __only__ exist as a result of an interaction
 * **Contact forces:** forces that result when the two interacting objects are perceived to be physically contacting each other.
 * Examples: frictional forces, tensional forces, normal forces, air resistance forces, and applied forces
 * **Action-at-a-distance forces** are those 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
 * Examples: gravitational pull, magnetic force, electrical force
 * Applied Force: a force that is applied to an object by a person or another object
 * Gravity Force: pull of gravity on an object, a.k.a. //weight//
 * Normal: support force exerted upon an object that is in contact with another stable object
 * Friction: force exerted by a surface as an object moves across it or makes an effort to move across it
 * **Sliding friction** results when an object slides across a surface
 * **Static friction** results when the 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
 * Air Resistance: air resistance is a special type of frictional force that acts upon objects as they travel through the air, often observed to oppose the motion of an object
 * Tension: force that is transmitted through a string, rope, cable or wire when it is pulled tight by forces acting from opposite ends
 * Spring: force exerted by a compressed or stretched spring upon any object that is attached to it
 * Net Force: the vector sum of all the forces that act upon an object
 * Net forces are present if there are unbalanced forces acting upon an object.
 * If forces are unbalanced, there is acceleration, meaning that a net force is present when there is acceleration

= Homework 11/17/11 = Lesson 3

**Parts a-b** Questions: 1.What is Newton's Second law? 2.What is the big misconception? 3. What is the logic behind the misconception?
 * the acceleration of an object is dependent upon two variables - the [|net force] acting upon the object and the mass of the object.
 * as the force acting upon an object is increased, the acceleration of the object is increased.
 * as the mass of an object is increased, the acceleration of the object is decreased
 * "The 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."
 * ===** **a = Fnet / m** **===
 * sustaining motion requires a continued force
 * To overcome this, we should view physics as a system of thinking about the world rather than information that can be dumped into your brain without evaluating its consistency with your own belief systems
 * Physics students come into physics class with a set of beliefs that they are unwilling (or not easily willing) to discard despite evidence to the contrary
 * Many times, people are thinking based on what they see, not based on the physics behind it.
 * To avoid this, think like a physicist and use your brain instead of just making assumptions.