Ch4_ChungA

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**Lesson 1 (a-d)**
1. What is Newton's First Law of Motion?

An object at rest tends to stay at rest while an object in motion stays in motion unless some outside force acts upon it.

2. What is inertia and what is mass?

Inertia is, put simply, the resistance of an object to changes in its motion.

Mass is the direct quantity that depends on inertia.

3. What does "state of motion" mean in the context of Newton's Laws?

State of motion means velocity, which is the change in speed. Inertia can thus be redefined to mean the tendency of something to resist changes in velocity.

4. What are balanced and unbalanced forces?

Balanced forces are when the various forces acting upon an object balance each other out to a point of equilibrium.

Unbalanced forces are the exact opposite of balanced forces. Something is acting upon an object that is not balanced out, which leads to a change in acceleration.

**Lesson 2 (a-d)**
1. What is force?

Force is essentially a push or a pull on an object. You can have contact forces and at distance forces. The difference between the two is that contact forces appear to have two objects touching each other while at distance forces do not.

We tend to measure forces through Newtons, which equal 1 kg x m/s^2.

Forces tend to balance each other. When they do not, acceleration occurs.

2. Explain the different types of forces. Also, explain the difference between mass and weight.

You can have contact forces, which are:
 * Frictional
 * Tension
 * Normal
 * Air Resistance
 * Applied
 * Spring

and At Distance forces, which are:
 * Gravitational
 * Electrical
 * Magnetic

The mass of an object refers to how much matter is contained by the object. The weight of an object refers to the force of gravity on an object. We sometimes measure gravity in G's, which varies from planet to planet.

3. What is a free body diagram?

Free body diagrams show us the relative magnitude and direction of all forces acting on an object. Each arrow has some type of force. You don't need to have four arrows in a FBD.

4. How do you determine net force?

Net force is the vector sum of all the forces acting on an object.

Net force plays into Newton's First Law of Motion.

**Lesson 3 (a-b)**
1. What is Newton's Second Law of Motion?
 * The acceleration of an object is based on two things: the net force acting on an object and the mass of the object. This only pertains to things that have unequal forces acting on them.
 * As the force acting on an object increases, the acceleration increases.
 * As mass is increased, acceleration decreases.
 * Equation is: a = Fnet/m or Fnet = ma
 * 1 Newton = 1kg * m/s^2

2. What is the big misconception? Why is it important in learning Physics?
 * The big misconception is that you need a continued force to sustain acceleration. This is simply not true. Forces cause acceleration, not motion.

**Lesson 3 - Vectors**
1. How do you add forces?

You can use the head to tail method to add vectors. The entire objective here is to get the net force of a vector. Essentially, once you draw out all the vectors you can get the sum by drawing an arrow from the tail of the first vector to the head of the second one. Also, net force is generally zero at equilibrium... which makes sense because it isn't going anywhere (thus the term equilibrium). If forces are unbalanced the object will undergo acceleration.

2. What is vector resolution of forces?

Essentially, you can break a vector up into two parts: vertical and horizontal. We can determine these components through the use of trigonometry.

3. What is equilibrium and statics?

When all the forces acting on an object are equal, the object is at equilibrium. A moving object can be at equilibrium because it just means that it isn't accelerating.

Static equilibrium is essentially when an object is at rest and not accelerating.

An object only accelerates when it is not at equilibrium... i.e. the forces acting on it are not equal.

4. What happens when we revisit net force equations and use diagonal forces?

The force at an angle can be resolved into two components that essentially replace the original force. This is especially handy because we can go back to the old school vector forces on an object that we know and love. We can subsequently find the acceleration by using the net force equations.

Also, bear in mind that the normal force acting up on an object and the y component must equal gravity if there is no vertical acceleration.

5. What happens when we bring in inclined planes?

Inclined planes have to do with tilted surfaces.

The rate at which the object slides down depends on:
 * the level of tilt

We call such a tilted surface an inclined plane

There are always two forces acting on an object on a tilted surface... gravity and Fnorm.

You must also divide the weight vector into two components.

You can then find these vectors using trigonometry. It is also important to remember that in the absence of friction, the acceleration is defined as: a = g * sin(x)

6. How would you go about solving two body problems?

You would find the acceleration that the objects have and the force acting between the objects.

You can use two different strategies to solve two body problems.
 * System analysis to determine the acceleration and an individual object analysis to determine the force between two objects.
 * Two separate analysis to determine two equations that can be solved using a systems of equation.

**Lesson 4**
1. What is Newton's third law?

Newton's third law is quite simple and states that for every action, there is an equal and opposite reaction. This can be extrapolated to free body diagrams. Whenever there is a force acting on an object, there will be a opposite reaction.

Force thus tends to come in pairs: action and reaction forces.

Consider the case of birds. As birds push down on air with their wings, the air pushes them back up. This is essentially how birds fly.

2. How do you identify action and reaction force pairs?

Identifying action and reaction force pairs is a simple process. Essentially, what you want to do is identify the two interacting objects and make two statements describing who is pushing on whom and in what direction.

**Notes**
11/15/11:

Inertia is a property that measures how difficult it is to change an object's motion; This is Mass

Weight is how much gravity is acting ON a mass

Mass is measured using (Kg)

Our SI units are Kg, m, and s

Weight is a force, pull of gravity on a mass (N)

Weight is different on each planet

w = m * g

Two Types of Equilibrium
 * 1) Static - at rest, no motion
 * 2) Dynamic - constant speed


 * Newton's Second Law: When an unbalanced force acts on an object, it will accelerate in the direction of the unbalanced force**


 * 11/17/11**

∑F = ma The x + y components are independent of each other

Net force of the F axis is equal to the mass times the acceleration of the x

∑Fx = m * ax

∑Fy = m * ay

Acceleration vs ∑F Graph is linear

Acceleration vs Mass Graph is a curve starting from a high A and low M to a low A and high M

Drop and Pull Setup: Newton's 2nd Law (ignoring friction)

a = ∑F/m

∑F = the force that is causing acceleration m = the total mass that is acceleration or that is being accelerated

In the drop and pull situation, what is the force that causes it to accelerate?
 * 1) Tension, caused by the weight of the mass being pulled downward

∑F = Mhanging * g

In a Drop and Pull Setup, both things accelerate

a = (Mhanging * g) / (M + Mh)

Push Pull Examples:
 * 1) Feather attached to Weight would be 9.8 m/s/s
 * 2) Weight attached to feather would be 0/m = 0


 * 11/18/11**

∑F = ma

∑Fx = m * ax
 * T-N1 = m * ax for a FBD with Tension to the right and N1 to the left (ON THE X)

∑Fy = m * ay
 * N2-W = m * ay