Ch4_LuoR

toc __**Newton's Laws**__ =__**Homework Summaries**__=

**Lesson 1A: Newton's First Law**
Q.) 1. What is inertia? 2. Where do we find inertia in everyday life?

R2.) 1. Inertia is a state in which objects continue to move at the speed it was launched at, and an object in inertia continues in a state of inertia until some outside force disrupts the state of inertia. 2. Some examples of where you can find inertia in everyday life are when you are in a car and also in an elevator. When breaking while driving at high speeds, your body will want to continue at those high speeds and refuse to stop. Your seat belt prevents you from continuing at such speeds, though, as it secures you safely to the car (if you have it on correctly) and your movements are in correlation to the the movements of the car. In an elevator, you can feel the blood rushing to your head every time the elevator descends, and the rushing of the blood in your head is due to inertia.

R3.) Newton's first law is the law of inertia. He stated that objects in motion will remain in motion and objects at rest will stay at rest. You can find this in everyday life, although you may not notice because of it happening so frequently. Your seat belt in your car keeps you safe from the law of inertia, as it prevents you from catapulting into your windshield every time you brake.

**Lesson 1B: Inertia and Mass**
Q.) 1. How did Newton's ideas contradict with other beliefs during his time? 2. How did Galileo pioneer the concept of inertia? 3. What is the relationship between mass and inertia?

R2.) 1. Many of Newton's contemporaries believed that objects had a natural tendency of coming to a stop. Newton's law of inertia contradicts that belief by saying that objects in motion will stay in motion, given that there are no outside forces affecting the object. 2. Galileo experimented with friction, and through his observations during the experiments, reasoned that if there was no friction, a dropped ball will attempt to achieve the starting height, and if there was no angle in which the ball returned up, the ball would continue rolling forever. 3. Objects resist changes to their state of motion, so a greater mass means the resistance to change will be even greater than a smaller mass.

R3.) Newton's law of inertia contradicted the ideas of his contemporaries. However, Newton only built on what Galileo originally theorized. Galileo speculated that if there was no friction, a moving object will continue moving forever. Newton took Galileo's speculations and experimented with them, eventually coming to the conclusion that an object comes at rest because of a present force, which is friction. Inertia changes between objects of different masses. Objects with a higher mass will be less apt to change its state of movement than objects of lower masses. For example, it is easier to push over a bike with a chrome frame than it is to push over a bike with a steel frame because chrome is lighter than steel.

**Lesson 1C: State of Motion**
Q.) 1. What is "state of motion"?

R2.) 1. "State of motion" is the velocity of the object in motion.

R3.) Inertia is the tendency of an object to resist a change to the state of motion, so its also means that inertia is the tendency of an object to resist a change to its velocity. For example, an object at 0 m/s velocity will want to stay at 0 m/s and an object at 37 m/s NE will want to stay at 37 m/s NE.

**Lesson 1D: Balanced and Unbalanced Forces**
Q.) 1. What is the difference between balanced and unbalanced forces? 2. What is meant when somebody describes an object to be at equilibrium in correlation with Newton's Laws?

R2.) 1. Balanced forces are when the forces acting upon an object negate each other so that the object does not accelerate in any form. Unbalanced forces are the opposite, so there is always some force causing the object to accelerate when talking about unbalanced forces on a object. 2. An object at equilibrium is when all the forces acting upon the object are balanced so it does not cause any acceleration.

R3.) Understanding balanced and unbalanced forces is essential in understanding Newton's Laws. Balanced forces are when the combined forces acting upon an object does not cause the object to accelerate, and the opposite is true for unbalanced forces. Forces acting opposite of each other cancel each other out, so there is no acceleration. Objects that have no acceleration are said to be at equilibrium, so objects with balanced forces acting on it are always at equilibrium.

**Lesson 2A: The Meaning of Force**
Q.) 1. What are the differences between contact and action-at-a-distance forces?

R2.) 1. Contact forces only occur when two interacting objects are perceived to be in physical contact with each other. On the other hand, action-at-a-distance forces are forces that are able to act upon objects even when they are not in physical contact with each other.

R3.) A force is defined as the push or pull upon an object resulting from an object's interaction with another object. There are two main categories of forces: contact forces and action-at-a-distance forces. Contact forces, such as friction and normal forces, only occur when two objects are in physical contact with each other. Action-at-a-distance forces, like gravitational and magnetic forces, can occur even without objects being in physical contact with each other. Forces are measured in Newtons (N), which are 1kg*(m/s 2 ).

**Lesson 2B: Types of Forces**
Q.) 1. What can effect "g's"?

R2.) 1. Variations of gravitational pulls can change g's. That is why weight can vary depending on where you are such as the moon and places on the Earth that has less gravitational pull than other places.

R3.) As explained in Lesson 2A, there are many types of forces that are a result of different kinds of interaction between two objects. Each force, though has its own symbol, that usually appears as a capitol F and a subscript that is an abbreviation of the type of force it is. For example, the symbol for friction is F frict . The differences of weight and mass are also explained in this passage. Weight is the force of gravity acting upon an object, while mass is how much "stuff" id in an object. That is why weight varies in different places on Earth and in outer space, where the gravitational pull exerted on an object varies greatly. However, mass will always stay the same no matter where you are because the matter in the object will never change unless broken apart. Along with gravity and mass, the differences between the two kinds of friction, sliding and static, are investigated in the passage. Sliding friction results when an object slides across a surface, while 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.

**Lesson 2C: Drawing Free-Body Diagrams**
Q.) 1. What is a free-body diagram?

R2.) 1. A free-body diagram is a special vector diagram that show the magnitude and direction a force or forces exert on an object.

R3.) Free-body diagrams are essential in understanding forces. These diagrams help show a person what forces are being exerted on an object and which direction the force is being exerted towards. This is important when solving equations dealing with forces because the diagram show you what you need to solve for and which forces are added or subtracted depending on the direction of the forces.

**Lesson 2D: Determining the Net Force**
Q.) 1. What is net force?

R2.) 1. The net force is the vector sum of all the forces that act upon an object.

R3.) Net force is the sum of all the vectors acting upon an object.

**Lesson 3A: Newton's Second Law**
Q.) 1. What is Newton's Second Law? 2. How does it pertain to the first one?

R2.) 1. Newton's Second Law pertains to the behavior of objects for which all existing forces are not balanced. It states that the acceleration of an object depends directly on the net force of the object and inversely on the mass of the object. The equation for acceleration here is a=F net /m, and thus net force is F net =a*m. 2. Newton's Second Law expands on the First Law to show what happens when forces are unbalanced.

R3.) Newton's Second Law is closely related to the First Law, as it expands upon what happens to an object when the forces acting upon it are unbalanced.

**Lesson 3B: The Big Misconception**
Q.) What is the big misconception?

R2.) The big misconception is that sustaining motion requires continued force.