CH4_SolimanoM

=toc Lesson 1 a-d Method 4=

What is Newton's First Law? - 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 on by an unbalanced force. -This predicts both objects at rest and objects in motion. -It will only change if it is forced to by an unbalanced force. -The motion above is constant speed in a straight line.

What are some applications of Newton's Law? -The behavior of liquid when moving in an automobile. The experience of a person when a car is braking. A brick is broken over one's head without feeling the break. Getting ketchup out of a bottle requires a thrust and stop.

How are both inertia and mass defined? -Inertia is the resistance an object has to a change in its state of motion. The inertia of an object is also dependent on its mass. The more inertia, the more mass of an object. -Inertia is a property, and is measured by its mass and is also how difficult it is to change an object's motion. This is mass, not weight. -Weight is a force, the pull of gravity on a mass. Mass is measured in Kg and weight is measured in Newtons. -Weight = m x g -Inertia is also the tendency to resist accelerations.

What did Galileo propose about inertia? -Galileo discovered that friction has a large affect on moving objects, by affecting their motion. He used an experiment involving a ball and two curved planes to show the effect of friction on the motion. Newton furthered this discovery by stating that a force is not needed to keep an object in motion. He found that a ball on a ramp will try and reach its original height and if it cannot it continue constantly.

What is an unbalanced force? -If normal force = weight, there is balance, and is called equilibrium. Static equilibrium is when there is no motion. Dynamic equilibrium happens when there is constant speed. In both cases, forces are balanced. -When an unbalanced force acts on an object, it will accelerate in the direction of the unbalanced force. -When N (normal) > W (weight) there is an increase in speed up, and an acceleration. An example is an elevator or decreasing a speed downward.

-sigma F means net force.

Class notes Inertia

What is Newton's Second Law? F = ma X and y components are independent of each other. Net force of (EF sub x) is m x a(sub x) Net force of (EF sub y) is m x a(sub y)

=Lesson 2 (a-d) Method 4= What is force? -A force is a push or pull on an object from the object's interaction with another object. Force only exists as a result of an interaction.

What are the two types of forces? -1. Contact forces: Occurs when two objects are physically contacting each other. Examples include frictional forces, tensional forces, and normal forces. -2. Action-at-a-distance: Occurs when two objects are not in physical contact and still exert a push or pull on each other. Examples are gravitational, electrical, and magnetic forces.

How is force measured? -Force is measured in Newtons. One Newton is 1 kg x (m/s^2). A force is also a vector quantity. Vector diagrams can be drawn, and can show whether forces are balanced or unbalanced.

Name and describe forces Applied: A force that is applied to an object by a person or another object. Gravity: The weight of the object; its force attracts another object to itself. Fgrav = m x g. On earth = 9.8 N/kg. Normal: The support force exerted upon an object that is in contact with another stable object. Friction: Force exerted by an object as another object moves across it, or tries to move across it. Air resistance: A frictional force on an object as it moves through air. It often opposes motion. Tension: The force transmitted through a rope, cable etc. It is directed along the wire away from the system. Spring: The force exerted by a compressed or stretched spring on any object attached to the spring.

Note: Weight is the force of gravity on the object. Mass is the amount of matter contained by the object. Weight varies based on force of gravity.

What is a Free Body Diagram? -An FBD is a drawing of the system under observation, which depicts the forces acting on the system with vectors. Objects do not always have a fixed amount of forces acting on the object. Forces include tension, friction, normal, and gravity.

How is Net Force determined? - The Net Force is the vector sum of all forces acting on the object. Because the FBD has vectors, the Net Force can be evaluated using them. Vectors can cancel each other, and through this we can determine whether the forces are balanced or not.

=Lesson 3 a-d Method 4= What is Newton's second law? -Newton's second law is in reference to objects which are not acted on by balanced existing forces. -The acceleration of an object depends directly upon the net force acting on the object, and inversely on its mass.

What is the equation for Newton's second law? -a = Net Force / Mass -It can also be rewritten as Net Force = Mass x accel. -A standard metric unit of force is 1 Newton = 1 Kg x m/s^2

What is the big misconception of Newton's second law? -Many can say what Newton's second law is, but do not know what it means. -Many students are adamant in their pre-recognized notions of motion and are unwilling to hear the true theories. -One notion that is sometimes not believed is the fact that a net, or unbalanced, force causes an acceleration, and the acceleration is in the same direction as the net force.

How is acceleration found? - Acceleration is determined by the equation a = Net Force/ Mass. When given a net force and a total mass, one can solve for the acceleration of a system.

How are individual forces of a system found? -By setting up free body diagrams and labeling individual forces, as well as setting up equations, one can solve for individual forces when given net force.

What is the relationship between free fall and air resistance? - the acceleration due to gravity, g, is 9.8. Objects free fall at the same rate, regardless of their mass. -By setting up FBD's and using Newton's second law, we can see that something with a larger weight may have a greater downward force, but its weight or force will offset it by its great mass, and thus will not have a real effect on its falling. -This ratio is known as the gravitational field strength.

How are two body problems solved? -These types of problems are characterized by two unknown quantities. Most commonly the acceleration and force between two objects is solved for. -These can be solved for by using a system analysis, where the two bodies are considered to be one, or by an individual object analysis, where the objects are isolated and solved for separately. FBD's are used and the forces are solved for. Combining these methods will yield results of these types of problems. -Another way of solving is by establishing the two FBD's and using Newton's second law to relate forces to mass and acceleration. The unknown values can then be solved with the equations.

**Lesson 4 Method 4** What is Newton's third law? -Newton's third law states that every action has an equal and opposite reaction. The size of the force between two objects (action-reaction pairs) is always equal. These forces always result from interactions, and are a push or pull that are caused by this interaction. -The direction of the equal forces are always opposite to each other.

What are some examples of action-reaction force pairs? -A fish swimming through water, because the fish pushes on the water and the water pushes back on the fish. -A bird pushes air downwards, and the air pushes the birds back up. -A car's tires push the road backwards, and the road pushes the car forwards.

How do you identify an action-reaction pair? -It is made by identifying the two forces that are reacting with each other and explaining the direction in which they push/pull on each other. -An example would be a ball hitting a bat, where the ball and bat are the action-reaction pair.

=Lesson 3 Vectors Method 4= How is adding vectors relatable to our current applications? -Our previous knowledge of adding vectors, notably the head to tail method of adding vectors can now be used with force vectors in many applications. For example, net force can be calculated by adding vectors, especially collinear vectors. The net force that is calculated can then be used to find the acceleration. -An object who's net force is 0 has balanced forces and is at equilibrium.

How are forces resolved? -Any vector having an angle an axis can be resolved into two vectors. These vectors are components. The components describe the influence of a force in a certain direction. -Trigonometric functions then can be used to solve for the influence of the force in the direction. The force should be of the same magnitude as its components, while the angle changes. -Net force problems may also require that vectors are resolved, so that one can solve for unknown forces.

What is equilibrium? -When all of the forces that act on an object are added up and they are balanced, they are in equilibrium. Individual forces may not always be equal, but they can still balance. -When in equilibrium an object will maintain its state of motion with the same speed and direction. -An object that maintains rest has static equilibrium.

How do inclined planes affect vector resolution? -A tilted surface is known as an inclined plane. The normal force no will be at an angle, as will friction and tension, if in the problem. Weight still points straight down. Weight can be resolved into vectors, and the unknown forces can then be solved for. -Without friction, a = g sin (theta)

How are two dimensional problems solved? -The problems under observance are usually connected by an object such as a string, and move in different direction. An example is a pulley system, where one objects moves downward, and the other to the right or to the left. In this example, they will share an acceleration. -To solve these, one needs to establish different axes systems for each object in the environment. When doing this, it is best to make both objects accelerate in the positive direction. Free body diagrams can then be constructed and Newton's laws can be used to solve for the unknown forces or accelerations.