Ch4_TalasH

= = =Newton's Laws - Lesson 1= a, b, c, d

A How are examples such as the behaviors of coffee in a coffee cup when filled to the rim related to Newton’s Law?

In a car, the state of the car will change (when the car moves from a rest position) due to an unbalanced force. However, coffee will want to say at rest and so it will then spill onto the drivers lap. This idea follows Newtons law where an objects at rest stays at rest unless acted upon an unbalanced force.

B What is inertia?

The resistance an object has to a change in its state of motion.

How was the popular theory that all objects would come to a rest position because of natural tendency proven wrong?

Galileo figured out that moving objects eventually stop because of a force called friction. When experimenting, he found that balls rolled to approximately the same height as the original. However, with a smoother surface, the ball would roll even closer to the original height because there would be no friction.

Do forces stop an object to a rest position?

Yes forces, such as friction, stop an object to rest position but do not keep it in motion.

Do some objects have more of a tendency to resist changes than others?

Yes, the tendency of an object to resist changes in its state of motion varies with mass. More mass = more inertia. This means that the object will resist changes in its state of motion more. toc C What is meant by the phrase // state of motion //?

The state of motion of an object is defined by its velocity; the speed with a direction.

D What is an unbalanced force?

When an object does not maintain its state of motion. Unbalanced forces cause accelerations.

What is equilibrium?

When two forces are of equal magnitude and in opposite directions. At equilibrium, an object will not accelerate and the object will maintain it's state of motion.

=Force and Its Representation - Lesson 2= a, b, c ,d

A What are some different types of forces?

Contact forces: two interacting objects that are physically contacting. Action-at-a-distance forces: there is no physical contact between two objects but there is still force.

What are some examples? What are forces measured by?
 * **Contact Forces** || **Action-at-a-Distance Forces** ||
 * Frictional Force || Gravitational Force ||
 * Tension Force || Electrical Force ||
 * Normal Force || Magnetic Force ||
 * Air Resistance Force ||  ||
 * Applied Force ||  ||
 * Spring Force ||

N (Newtons)



B What is weight?

The weight of an object is the force of gravity acting upon that object. Mass never changes no matter where it's located, but weight does.

Fgrav = m * g where g = 9.8 N/kg (on Earth) and m = mass (in kg)

What are the two types of friction?

static friction: when the surfaces of two objects are at rest and the force resists the movement of the object. Has a higher coefficient of static value than sliding friction.

sliding friction: when an object slides across a surface μ = coefficient of sliding friction
 * Sliding Ffrict = μ • Fnorm**

C What is the purpose of a free body diagram?

It is used to show the relative magnitude and direction of all forces acting upon an object in a given situation.

D What is a net force?

The vector sum of all the forces that act upon an object.(an unbalanced force)

How do you determine a Net force?

To determine the net force, you have to add all the individual forces acted on an object. = = =Newton's Second Law of Motion - Lesson 3= a, b

A What is Newton's second law?

The acceleration of an object is dependent upon two variables; the net force acting upon the object and the mass of the object.

What is the equation for net force and when do you use it?

Fnet = m * a

Why do net force and acceleration point in the same direction?

This is because acceleration is directly proportionate to the net force. For example, when a person is descending in an elevator (velocity is negative) and he/she is coming to a stop, he/she will feel the force (net force) acting on his/her feet going up when acceleration is also up.

B What is a common misconception for physics students?

The idea that sustaining motion requires a continued force. This is wrong because a force, such as friction, is needed to stop an object from moving; forces are not needed to keep an object moving.

Do forces cause motion?

No, they cause acceleration. An object could have its vertical forces balanced but may have a horizontal force going at constant speed.

REVIEW*** What does Newton's first law of motion say?

A force is not needed to keep an object in motion.

=Lesson 3 - Forces in Two Dimensions= 12.6.11 a, b, c, d, e, f


 * A**

How do you determine the vector sum of forces?

One can use the head to tail method where a scaled diagram is used to find net force. It is created by drawing the head of where one vector ends and the tail of where the next vector begins. When they are all added, the resultant is found.


 * B**

How do you resolve a vector at an angle?

One would have create two components. A Y and an X component .


 * C**

What is equilibrium?

When forces are considered to be __balanced__ if the rightward forces are balanced by the leftward forces and the upward forces are balanced by the downward forces; usually at rest or constant speed. The net force would be zero and the acceleration is 0.

Ex)

What is static equilibrium?

When an object is at rest in a state of equilibrium.


 * D**

How do you solve net force-acceleration problems?

One would have to use newton's second law to split the force vector into 2 components and then use sin and cos for the given angle and then solve for the unknown.

Ex) Determine the net force and the acceleration > Fnet = 129.9 N, right - 60 N, left = 69.9 N, right The mass is > m = (Fgrav / g) = 20 kg So the acceleration is > a = (69.9 N) / (20 kg) =3.50 m/s/s.


 * E**

How do you solve a problem on an inclined plane?

The normal and weight forces act on an object on an inclined plane where weight goes in a downward direction and the normal force is directly perpendicular to the surface. In the absence of friction and other forces, one could use the equation a=g*sin(theta) to solve a problem like this. However, usually one must split the weight into x and y components making the vector of the weight the hypotenuse of the right triangle that has been created.


 * F**

How do you solve a two system problem?

First, one would have draw free body diagrams for each system for clarification and understanding. Then, one must use newton's second law equation, Fnet = m•a. This can be applied to both diagrams in order to write two equations for the two unknowns. The Fnet will be expressed as the force in the direction of the acceleration minus the one that opposes it.

Ex)





Now one can solve by using substitution for the equations.

However, one can look at the problem as an entire system and use the equation a = net force / total mass.