Ch4PolewayM

toc //Chapter 4//

= = = = =Lesson 1- Newton's First Law of Motion=

__What is Newton's First Law and what does it do?__

- This law is known as the law of inertia, and it states that 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. - There are two parts to this statement, as this law deals with object in motion and objects that are stationary. - Objects continue to do what they are doing and they will not stop. If an object is in rest it will stay in rest. If its in motion it will stay in motion.

The first section talks about Newton's First Law, also known as the law of inertia. It tells that an object in motion will stay in motion and that an object at rest will stay at rest. IT then goes on to give real life situation of how the law of inertia is seen in everyday life. For example, it talks about a car braking and how the seatbelt works.

__What is inertia and how are mass and inertia related?__

- Inertia is the tendecny to resist changes in the state of motion - Friction is the force that causes moving objects to stop. If a ball was rolling, it would roll forever with no friction. - Forces aren't required to keep an object in motion. If you push a book, it will slide farther without you pushing it. - Mass is the quanitity that is solely dependent upon the inertia of an object. The more inertia there is, the more mass there is.

This section talks about what inertia actually is, as it is the tendency to resist changes in the state of motion. Galileo did an experiment and learned that the force that stops something from continuously moving is friction. Without friction, things could move forever. It was also stated that forces don't need to keep objects moving, as they continue to move on their own. It then describes the relationship of mass an inertia, as inertia is greater so is mass. There are more examples at the end of this section.

__How do you define the state of motion?__

- The state of motion is described by its velocity - Velocity is speed with direction - Inertia can now be described as the tendency to resst changes in velocity. - Object at rest has zero velocity - In object in motion will continute to have the same velocity unless acted upon by an unbalanced force.

This section talks about how the state of motion is velocity, which we already learned about at the beginning of the year. Now that they taught us about velocity, we could restate the phrase of inertia to make it better, changing "state of motion" with "velocity". Inertia is the tendency to resist changes in velocity and acceleration.

__What are the different types of balanced and unbalanced forces? What's the difference between a balanced and unbalanced force?__

- When forces balance each other out because they have equal magnitudes and point in opposite directions, the object's in equilibrium. When its at equilibrium it doesn't accelerate and stays at a constant speed, meaning there's no unbalanced forces. - free body diagram- shows that forces acting upon the object - Unbalanced forces cause the object to change its motion. cause acceleration

This section states that if two forces balance each other out and are pointing in opposite directions they are in equilibrium and are balanced. They don't cause any change in acceleration and the object is either at rest or constant speed. On the other hand, if there is an unbalanced force, say friction that nothing else can balance out, then the object changes its acceleration and motion.

=Lesson 2- Force and its Representation=

__What is a force, what's it used for, and what types are there?__

- a force is a push or pull on an object resulting from that object's interaction with another object. Forces only exist in an interaction. - There are contact forces, and forces resulting from action at a distance. - Combat forces are when they are physically touching each other, and these are frictional forces, tensional forces, normal forces, air resistance forces, and applied forces. - At a distance forces still create a push or pull even if they aren't physically touching each other and these include gravitational forces, magnetic forces, and electrical forces. - Newtons are the units of forces, and they are what gives a kg an acceleration of 1. - Forces are vector quantities so they deal with magnitude and direction

Forces are introduced in this section and it gives the defintion of what they are. They are pushes or pulls on objects resulting from the interaction of another object. Forces are grouped into two groups, combat and at a distances forces. Forces are vector quantities and can be shown in free body diagrams as explained a little at the end, and they are shown in Newtons.

__What are the different forces and what do they do? What's the difference between mass and weight?__

- Applied force- a person applies their force to an object - Gravity force- when an object is forced towards a larger object like the moon or earth - weight is used in the gravity force, and it is mass times gravity - Normal force- a force that is acted upon an object by another stable object like the ground exerting force on a block - Friction force- a force that is exerted by a surface as an object moves across it. Friction usually slows things down. - Air resistance force- a type of frictional force that acts upon an object as it travels through air. If there was no air resistance all objects would travel at the same speed - Tension force- a force that is trasmitted through a string, rope, or cable when it is pulled tight from forces acting on opposite ends - Spring force- force exerted by a compressed or stretched spring upon an object acting on it.

This section basically goes into detail about each force in our world, ommitting electrial and magnetic forces. These forces include all the above in the notes and when gravity force came we learned about weight. Weight is mass time gravity and it is the amount of gravity acting upon it where mass is the amount of matter contained in the object.

__How do you draw free-body diagrams?__

- Used to show the magnitudes and directions of all forces acting on an object - Boxes are usually used in these diagrams with arrows coming out from the center showing which direction they're going - Size of arrow determines magnitude. - Where arrow is pointing shows direction of the force - If there are two or more arrows for the same type of force then use subscripts to describe them.

Through this section we learn what the free-body diagram is used for and how to draw it using arrows and a box. There's a list of all the force names that are used in these diagrams. Arrows show magnitude and direction, depending on how big they are and where they're pointing

__How do you determine net force__

- the net force is the vector sum of all the forces acting upon it. - you find the net force by simply adding all the vectors together - If the forces are balanced then there is not net force, but if they are unbalanced then there is a net force which causes acceleration.

The net force is the vector sum of all the forces acting upon, and obviously to find it, you add all the vectors together. If the vectors are balanced though, as forces of the same manitude and opposite directions cancel each other out, then there is no net force. If there is an unbalanced force, then it causes acceleration and we are able to find a net force. There are several examples that help you understand this after the reading.

=Lesson 3- Newton's Second Law of Motion=

__What is Newton's Second Law? What does it state and how is it used?__

- The second law states the acceleration is dependent on the net force acting upon the object (directly) and the mass of the object (inversely). As the force increases so does the acceleration, and as the mass increases, the acceleration decreases.
 * Fnet = m * a**
 * -** The net force is related to acceleration, not any other type of force. The net force is the vector sum of all the forces.

This section tells us what the second law is, as acceleration is dependent on two different factors. It directly depends on the net force and inversely on the mass of the object. It gives us the basic equation used to find the force, mass, or acceleration if the other two are given. The net froce must be used though, and not just an force can.

__What is the big misconception of Newton's Laws and what is actually true about it?__

- A big misconception is that continuing motion requires a continued force. We know this is very wrong though - Net forces and unbalanced forces cause acceleration, not motion - Net force and acceleration are always going the same direction

Many people believe that sustaining motion requires a continued forces, which is SO wrong. We know this and net forces and unbalanced forces are what cause acceleration. They don't cause motion though. In addition, net forces and acceleration always go and point in the same direction. An object would always be in motion if there was no friction. Friction causes these objects to slow down, which is why many people think that without a continued force, an object will stop.