Unit Blog Reflection: Unit 3: Momentum, why do airbags keep us safe?

This unit was about Newton’s third law, which says that for every action there is an equal and opposite reaction. The unit was sectioned off into categories which include action and reaction pairs, momentum and its relationship to force, forces in perpendicular directions, gravity and tides, and the conservation of momentum.

According to Newton's third law, for every action force there is an equal and opposite reaction force. Forces always come in pairs - known as "action-reaction force pairs." Identifying and describing action-reaction force pairs is easy all you have to do is simply identify the two interacting objects and make two statements describing who is pushing on whom and in what direction. For example, consider the interaction between a horse drawn carriage (known to my class as the horse and buggy problem). Why is a horse able to pull a carriage? To answer problems of this sort (bouncy floors for gymnast) you must make sure to keep the same verb, directions must be opposite of each other, and the subjects have to stay the same. First we were to label all action and reaction pairs.

1.      Horse pulls buggy forward, buggy pulls horse backward.

2.      Buggy pushes ground forward, ground pushes buggy backward.

3.      Horse pushes ground backward, ground pushes horse forward.

 you must use this information to answer the reasoning behind why the horse is able to move the buggy. The horse pulls buggy with an equal force that the buggy pulls with. We know this because of Newton’s 3^rd law which says every action has an equal and opposite reaction. The horse and buggy move forward in the horse’s direction because the horse pushes the ground harder than the buggy pushes on the ground. The horse is able to move the buggy because of its hooves which allow for friction on the ground over the wheels.

The next thing we discussed in class was vectors in particular were adding non- parallel vectors/ and free body diagrams. The best example is which boat would get across the river first? The answer is a. We know this because we draw vectors with each arrow already provided to create a parallelogram and then connect the boat the farthest corner. A is the only option which moves with the current and goes straight across when the vectors are drawn.
We followed this section with force of gravity and tides. We learned the relationship between the force and gravity equals F=G(m₁m₂)/d². So if distance decreases the force increases and if distance increases the force decreases. So, if the distance is doubled the force decreases by 1/4, and if you cut the distance in half you force increases by 4 times its original. We also learned about how tides are caused and which has the greater force: the earth and the huge sun or the earth and the closer moon. We learned that to calculate the force between the sun and the earth and the earth to the moon we had the use the equation F= G(m₁m₂)/d², and then we plugged in. We learned that the greater force is between the earth and the sun and confused many of us including myself on how tides are caused. Tides are caused due to the location of the Earth. They are caused by the difference in force which is greater than the sun to the earth. They are caused by the difference in force felt by opposite sides of the Earth. We also learned that distance has a greater effect on the force than a change in mass and that everything with mass attracts everything with mass, and everything with mass has a force. This also relates to your weight on earth, so the closer you are to the center the smaller you are and the farther away you are the more you weigh. There are two types of tides; they are spring tides and neap tides. Spring tides are higher high tides and lower low tides. Spring tides occur when the sun and the moon are aligned. Neap tides are high low tides and the lower tides are higher. Neap tides are when the moon is perpendicular to the Sun and half-moons.
The next section focused on Impulse and its relationship to momentum. This section focuses on the big question; how airbags keep us from getting injured (or less injury). p=mv, and the change in p or delta p= pfinal-pinitial. P represents the momentum. The change in p is the same regardless of if you stop quickly or slowly. Impulse is force * time the force is applied. Impulse is represented by J. So J=F * change in time, or J= change in p. This section also related to; why are nylon ropes which stretch considerably under tension, favored by mountain climbers? The answer is; no matter how a person falls they go from moving to not moving (p=mv). Therefore the change in momentum is the same regardless of how they are stopped. (deltap= pfinal- pinitial). Since the change in p is the same no matter how it is stopped the impulse is also the same (deltap=J).The climber prefers nylon ropes because they are stopped over a longer period of time rather than being stopped right away (J=F*deltat) (J=-F*deltat). This causes the force on them to be smaller, the smaller the force the less likely to be injured.

Momentum is a commonly used term in sports. A team that has the momentum is on the move and is going to take some effort to stop them. Momentum is a physics term; that refers to the quantity of motion that an object has. If an object is in motion (on the move) then it has momentum. Momentum can be defined as "mass in motion." All objects have mass; so if an object is moving, then it has momentum - it has its mass in motion. The amount of momentum that an object has is dependent upon two variables: how much stuff is moving and how fast the stuff is moving. Momentum depends upon the variables mass and velocity. In terms of an equation, the momentum of an object is equal to the mass of the object times the velocity of the object. Momentum = mass * velocity. We then focused on the conservation of momentum. The conservation of momentum relates to Newton’s third law in that it is the absence of an external force, so if you wish to change the momentum of something you must change the momentum of the entire system. The more momentum that an object has, the harder that it is to stop. Thus, it would require a greater amount of force or a longer amount of time or both to bring such an object to a halt. As the force acts upon the object for a given amount of time, the object's velocity is changed; and hence, the object's momentum is changed. Force acting for a given amount of time will change an object's momentum. One focus of this unit is to understand the physics of collisions. The physics of collisions are governed by the laws of momentum; and the first law that we discuss in this unit is expressed in the above equation. The equation is known as the impulse-momentum change equation. The law can be expressed this way: In a collision, an object experiences a force for a specific amount of time that results in a change in momentum. The result of the force acting for the given amount of time is that the object's mass either speeds up or slows down (or changes direction). The impulse experienced by the object equals the change in momentum of the object. In equation form, F • t = m • Δ v. In a collision, objects experience an impulse; the impulse causes and is equal to the change in momentum. Collisions in which objects rebound with the same speed (and thus, the same momentum and kinetic energy) as they had prior to the collision are known as elastic collisions. In general, elastic collisions are characterized by a large velocity change, a large momentum change, a large impulse, and a large force.

What I have found difficult about what I have studied is getting the big picture and relating it to the real world in real word terms. I overcame these difficulties by discussing the material with my teacher and my peers who were well aware of the concepts. I also overcame these difficulties by beginning to explain bits and pieces to my peers and them filling in parts of the bigger picture for me. What made the lightbulb click?  Well for one I’m unsure if there was even a lightbulb. I kind of just walked through the motions and for most of each section felt lost until I revisited my notes and course videos. My goals for the next unit are to review my notes after class and section and to ask for help sooner than later so that I am more prepared for test and quizzes. My problem-solving skills have improved in my opinion but I could still work on formulating my arguments to help my answers. My effort grade should be a 4 or 5 because I work very hard, by asking questions, helping my peers and being tentative.  My learning in general needs to be worked on just by reviewing my notes sooner and preparing myself by possibly making note cards and familiarizing myself with the big pictures of each unit. My persistence has been found in my questioning and my answering of proposed questions. My self- confidence in physics is really low because I feel like I know the information than I sit in front of the test or quiz and pretty much blank.          

Minute Physics- Tides

Recently in Physics we (the scholars) have been reintroduced to tides. This reintroduction included the reasoning behind tides and why they occur. The past few weeks I have found Minute Physics on Youtube extremely helpful which is why i chose this source. This source recaps what we have recently learned, beginning with why there are two high tides and two low tides a day. The video goes on to  explain why if the moon were to get any closer to the Earth the forces from Earth wound cause rocks on the moon to move and result in falling on the Earth.  

Unit blog Reflection

Do not be afraid of the title of this unit, it only applies to part of this unit.

In Unit 2 my class and I entered the world of Newton’s second law, which incorporated falling through the air which is SKYDIVING (has air resistance), free fall: falling straight down, throwing things straight up, falling at an angle and throwing things up at an angle. We also subconsciously learned how Newton’s first law and Newton’s second law relate.

Acceleration is the rate at which velocity changes with time. (image) Acceleration is produced by force. These concepts are connected using mass, thus the parts of Newton’s second law. Newton’s second law is a=f/m, which translate to acceleration is directly proportional to force and inversely proportional to mass. Therefore, if force were to increase acceleration would increase and mass would decrease. The acceleration applied to an object depends on applied forces, friction forces, and the inertia (unit 1) of an object. The amount of inertia an object has depends on its mass. The more matter an object has the more inertia. Mass corresponds to our intuitive notion of weight, but weight and mass are not the same thing. Mass is the quantity of matter in an object. It can also measure the inertia that an object exhibits in response to any effort made to start it, stop it, or change its state of motion in any way. Weight is the force upon an object due to gravity. In the absence of acceleration mass and weight are directly proportional. This means that if mass were to increase so would weight. When expressing the equation for acceleration one must also know the units, which stay constant: Newton’s (N) for force, kilograms (kg) for mass and meters per second squared (m/s²) for acceleration.

Acceleration= net force/ mass or a= fnet/m

With the application of direction the result will be a combination of speed change and deflection. Remember: the acceleration of an object is always in the direction of the net force. (i.e.- applied in the direction of the objects motion, a force will increase the objects speed)

Newton’s second law provides an explanation for Galileo’s concept of why objects of various masses fall with equal accelerations. A falling object accelerated towards the Earth because of the gravitational force of attraction between the object and Earth. An object is in a state of free all when the force of gravity is the only force action on it meaning air resistance is negligible. The greater the mass of an object the greater the gravitational force. Acceleration of an object depends not only on the force but also on the objects inertia. Remember: Force produces acceleration and Inertia is resistance to acceleration

The acceleration due to gravity is symbolized as g. Therefore g=f/m

Newton’s laws apply for all objects, whether free falling or falling in the presence of resistive forces. The idea of net force is important when discussing acceleration. In cases in which air resistance can be neglected, the net force is the weight because it is the only force. In skydiving once you leave the plane there are only two forces acting on you: the Earth's gravity pulling you straight down, and friction with the air. The friction with the air adds up to push you in the opposite direction of the direction you were originally going in. Air resistance increases as your speed increases, so when you drop you are moving slowly and gravity is stronger than the air resistance so you begin to speed up, accelerating towards the ground. However the faster you drop, the stronger the air resistance is and so eventually you are moving so fast that the air resistance is equal in strength to gravity and you no longer accelerate. You have reached terminal velocity. Why does body position come into it? Air resistance also depends on the shape of the object, so by tucking in your arms and legs you can reach a faster terminal velocity than if your arms and legs are spread out. Air resistance is affected by speed and surface area, which are directly proportional. As you fall you speed up and it causes you Fnet to decrease. After you open your parachute you Fair resistance increases, your net force is no longer on, and both your acceleration and velocity will decrease. Your major goal when skydiving is to be in equilibrium. The purpose of a parachute is to slow you down so you don’t gain more and more speed and implode the earth. A free falling object is an object that is falling under the sole influence of gravity. Any object that is being acted upon only by the force of gravity is said to be in a state of free fall. There are two important motion characteristics that are true of free-falling objects: Free-falling objects do not encounter air resistance, and all free-falling objects accelerate downwards at a rate of 9.8 m/s² (often approximated as 10 m/s²). Because free-falling objects are accelerating downwards at diagram of its motion would help in depicting acceleration. The fact that the distance that the object travels every interval of time is increasing is a sign that it is speeding up as it falls downward. The distance formula, for falling, is D=1/2(g)(t)2 and the velocity is V=(g)(t). Our study took us next to throwing things straight up and down. This concept asked for us to useD=1/2(g )(t)2 to find the time that the ball is in the air. However, we can only use this formula for the fall not the rise so we must double it to find the total time in the air. These concepts can be hard but one must draw pictures, which make it easier. The next section we learned was falling at an angle. A new equation was needed for the horizontal velocity, and it was V=d/t. We also need to know that the horizontal velocity does not effect the time something is in the air that is only affected by height/ distance upwards and downwards. During this section we learned that to drop a package we must drop it before the target as the plane moves. To find the where the package will land we had to use both the horizontal and the vertical equations to find where the package would land, if there is no air resistance on the box on its way down. Finally, we studied throwing things up at an angle. Three equations were needed for this section from before to find the horizontal and vertical velocities. However, we needed to find the actual velocity of the object by using the Pythagorean theorem, which says a²+b²=c². The equations we needed to memorize in order to understand this were triangle tricks. They are a triangle with two sides of 1 the third will be 1 root 2 which equals 1.41. If we multiply all by 10 or 100 we would just have 14.1 or 141. The last triangle is a 3,4,5 triangle which has two sides that are 3 and 4 and the hypotenuse is 5. The downward acceleration will always be 10m/s² and at the top of its path, the horizontal velocity will still continuing to push it forward. I found a lot difficult during this unit. My difficulties stemmed from lack of full concentration. I didn’t full understand free fall and throwing things up at an angle. Adding the component of horizontal and vertical were where I struggled the most. I overcame these difficulties by trying more examples and revisiting the videos. I huge help for me were my peers mainly Kaylee and Elise who were able to bridge gaps for me as well as me for them. My problem solving has definitely improved this unit. I believe I have gotten better because I’ve had to tweak my learning style with these new and different concepts, which expound off one another. My effort has also improved because I’ve been doing more than I’ve been doing, I engage more in class whether its too help myself or to help and a classmate. I’VE realized that when I know what is going on I have a way better experience because I can explain to others. My learning style has gotten deeper for I have realized I need to dig deeper to actually understand what is going on. My goals for the next unit are to use my prior knowledge with this unit and make more connections. I wish to improve my quiz grades by studying differently and attending conference period where maybe I can also receive helpful hints and ways to grasp the information to a fuller extent. One may connect this to everyday life because of sports. I am really into sports basketball and volleyball in particular. These sports I have realized are based on angles and arcs and someone this has also clicked for me on the courts. This unit also reflects baseball and how certain angles can help baseball players hit home runs. 

Free Fall Resource

 As of recently my physics class and I have been exploring the world of free fall and how physics has anything to do with it. This video discusses free falling objects and how this is physics. It explores how to answer the questions as well as how to perform the equations which we discussed in class. It informs the viewer that free fall is one dimensional motion. This video has helped me and should help others piece together the real world and physics.

Newton's Second Law

What is Newtons Second Law? Newtons Second Law is

Unit Blog Reflection

Paul G. Hewitt the creator/ editor/ author of my textbook said "the main reason to study physics is to enhance the way you see the physical world." When I first read this quote I was unsure what he actually meant and it is still not completely instilled in my brain. Everything I have learned so far has aided in the quote being plastered in my mind, because already things that I see on a regular basis have changed. Hewitt goes on to say to us as students that we " will see the equations as guides to thinking." I agree with this quote because at first I didn't understand the equations but as soon as real life examples were used I understood them. Already things that I have seen before I connect with what I am learning so I can better understand it. I am pumped to learn learn more physics (maybe I spoke to soon), but in order for myself and you as a reader to understand
In this unit I learned many things , which I've realized most I already Kind of knew. 

This unit began with inertia and Newton's first law. What many people don't know is that inertia and Newton First Law is all around us and are probably apart of something we couldn't fathom before like when dishes are on the table and the tablecloth is pulled from underneath it. Inertia is the resistance of any physical object to any change in its motion (including a change in direction). In other words, it is the tendency of objects to keep moving in a straight line at constant linear velocity, or to keep still.The big problem/ re-occuring problem for this section was why does an object stay still or kept moving.

ex. The dishes are at rest on the table. When the tablecloth is quickly removed it does not exert any force on the dishes and so the dishes remain at rest. We know this because of Newton's First law which says that an object at rest stays at rest unless acted on by an outside force. No force on the dishes results in the dishes staying at rest.


Another example of inertia is hovercraft riding. In an earlier post I explained my experience and what I learned through the experience. In this lab I learned and experienced the other part of Newton's first law which says an object in motion stays in motion unless acted on by an outside force.

 

In this unit I also learned I also learned about equilibrium and net force. I was able to experience these first hand while also completing the hovercraft lab. Net force  is the force on an object was shown and experienced in this lab by the starting point which by one pushing the hovercraft forward exerted force and when it got to the other end someone pushing it in the opposite direction first slowed it down its momentum then propelled it back towards the starter. Equilibrium was exemplified in the lab through resting place and where there were no forces acting on it and in phase 2 which was when it was gliding. 

Speed, velocity, and acceleration were also huge parts of this unit. Speed is the magnitude of velocity. Velocity is the rate of change of the position of an object. Many including myself confuse speed and velocity for each other but they are different. Velocity requires a specific direction while speed does not. So IF SOMETHING IS CHANGING DIRECTION IT IS ALSO CHANGING VELOCITY. When velocity changes that is known as acceleration or deceleration.  This means that acceleration is the change in speed, direction, or both of an object. We also learned the equations which go along with this unit which are:
constant velocity = distance/time
constant acceleration 
      how far: d= 1/2 at^2
      how fast: v=at
for finding the change in velocity one uses the equation a= change in v/ time
The big question posed in this section was what is the difference between constant velocity and constant acceleration.  Constant velocity I now know is something that doesn't change in speed or direction, and constant acceleration is the change is of velocity. Acceleration is gaining speed while velocity keeps a constant speed unless a change in direction occurs.

There were many things that were difficult for me to understand at first. They included constant velocity and how it affected acceleration, which I have already explained. I also didn't quite understand how velocity could go forward and acceleration go backwards. 

My problem- solving skills are fairly the same because I've always been taught to think and express things for myself. Now I just need to apply myself more so I could understand better. 

My goals for the next unit are to push myself, ask more questions, and to take more opportunities. 



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Comparing Constant Velocity to Constant Acceleration

Recently my class and I have been taking part in a lab which purpose is to help us understanding the differences between constant velocity and constant acceleration. The lab did this by closely showing how they measure different things and have different equations. This lab actually helped me understand the difference between the two. Constant velocity I now know is something that doesn't change in speed or direction, and constant acceleration is the change is of velocity. In this lab my partners pushed a ball on a flat surface and recorded its distance every half second, which we then graphed using the data we found using excel, which then gave us the equations of the line. Then we raised two legs on the same side of the table to make it a ramp and proceeded with the same steps as before. This helped us see that constant velocity and acceleration are similar but at the same time different because acceleration is gaining speed while velocity keeps a constant speed unless a change in direction occurs. The equation we used in the lab for velocity v= d/t, and for finding acceleration we used: how far- d= 1/2 at^2, how fast- v=at. When graphing the data found from measuring acceleration and velocity we realized that  constant velocity always had a straight trend line because velocity doesn't measure speed and that the acceleration lines curved because that shows the change in speed. This lab taught me or rather helped me better realize the difference between acceleration and that a lot of math which I have used before can be used in the equations of line such as y=mx+b. I also learned that it is better to know all the equations because then you can tell which is better to use for a certain project.

Acceleration and Velocity

Acceleration is a vector quantity that is defined as the rate at which an object changes its velocity. An object is accelerating if it is changing its velocity. Acceleration has to do with changing how fast an object is moving. If an object is not changing its velocity, then the object is not accelerating. Velocity is a vector quantity that refers to "the rate at which an object changes its position." An example is a person moving rapidly - one step forward and one step back - always returning to the original starting position, it would result in a zero velocity, because the person always returns to the original position, the motion would never result in a change in position. Since velocity is defined as the rate at which the position changes, this motion results in zero velocity. If a person in motion wishes to maximize their velocity, then that person must make every effort to maximize the amount that they are displaced from their original position. Every step must go into moving that person further from where he or she started. For certain, the person should never change directions and begin to return to the starting position. This video uses examples to show how this information relates to the equations used to find them.

Hovercraft Riding

Who knew Physics could be so fun? so far.....

              Thursday September 12,2013 my classmates and I experienced the joy of hovercraft riding. Riding a hovercraft is a bit scary because the rider has no control over the way the hovercraft moves and whether or not it starts and stops. The ride was also exhilarating and new, it was great experience over all. Riding a hovercraft is different from any other "vehicle" because it "hovers" over the ground, by not touching the ground there is no friction, the frictionless environment means that starting and stopping the hovercraft are impossible unless acted on by an outside force. 
              This hovercraft lab was created to help us understand basic physics concepts. These concepts include inertia, net force, and equilibrium. Through the lab process we got to experience first hand both parts of Newton's first law, which is inertia. Newton's first law states an object in motion stays in motion unless acted on by an outside force, and an object at rest stays at rest unless acted on by an outside force. Net force which is the force on an object was shown and experienced in this lab by the starting point which by one pushing the hovercraft forward exerted force and when it got to the other end someone pushing it in the opposite direction first slowed it down its momentum then propelled it back towards the starter. Equilibrium was exemplified in this lab through resting place and where there were no forces acting on it and in phase 2 which was when it was gliding. 
              Based on this lab:
     - acceleration seems to depend on the force from  one direction.
     - one can expect to have constant velocity after the acceleration phase when there is no longer force. 
                This lab also proved that inertia ( Newton's first law) works with the mass of something. I know this because some members were harder to start and stop than others because of their mass and weight distribution on the hovercraft. The hovercraft lab was fun to be both a starter and a rider, if anyone ever has the opportunity of this experience take it and have fun.
               
 

Inertia Resource

What is Inertia? As a viewer in need of a last minute comprehension lesson these videos recap what my class and I have recently learned about Inertia and Newtons First Law.  
Newton's first law of motion states that "An object at rest stays at rest and an object in motion stays in motion unless acted upon by an outside force." Objects tend to "keep on doing what they're doing." In fact, it is the natural tendency of objects to resist changes in their state of motion. This tendency to resist changes in their state of motion is described as inertia. Inertia: the resistance an object has to a change in its state of motion.

A Whole New World

         This school year will be the first year I attempt to explore the world of physics. This blog is my aid to others having the same experience, to know that there are other people struggling with physics concepts. I believe that studying physics is important because it helps us to understand the world around us, it helps one to increase their knowledge and find interest in things they've never even thought to question about, and physics can help me to understand and maybe even improve my athletic abilities.
          In physics this year I expect to learn many things, especially about gravity, centrifugal force, and tangential force, which my brother and his classmates from last year spoke abut often. I would also like to learn how physics applies to the sports I enjoy playing.  
          I have many questions which I continue to flip around in my head about physics class this year. The questions I have are how does physics play  its part in sports?, how does physics work in the use of credit card machines? , and what types of experiments will my class and I take part in?
          My goals for this school year are to understand the information so as to make it comprehensible to others , improve my science grade and show improvement throughout the entire school year , and to become a deep learner, (suggestion by my teacher) which means to not just scratch the surface of learning but to dig deep in understand and work ethic.