Work, Energy and the Conservation of Energy

Work, Energy and the Conservation of Energy

Work is any change in energy. 

Formula for work: Force x Distance

Units: Newton x meter = Joule

Conservation of Energy: in an isolated system, energy will be conserved. (Total Ein = Total Eout)

Gravitational Potential Energy: energy given to an object in a gravity field/ energy's position in gravity. (mass x gravity x height)

Kinetic Energy: energy of motion (1/2 mass x velocity^2) 

Power: rate at which work is being done. (change in energy/ change in time) (units: watt)

In the example above, it shows a pillow being kicked off  a flight of stairs, what exactly is happening in this system? Well, my sister (person kicking the pillow) is applying energy to the pillow thus giving it energy. See what's happening is the energy being applied to the pillow is being taken from my sister. The work of the pillow will be determined by the force applied to the pillow along with the distance it traveled. Now, when the pillow left the ground and started to fly down the stairs it gained something called gravitational potential energy, or energy of position, which is the pillows position in gravity. Now while the pillow travels down to its destination is gains something called kinetic energy, which is the energy of the motion, and it loses potential energy. The rate at which all of this is being done is called power. 

Momentum

Momentum

Momentum, as described in the Webster's dictionary, is the strength or force that something has when it is moving. We use the letter P to describe because m is used by mass and getting those two things confused is so not the haps.  

Formulas Used in Momentum:

Momentum (P) = m (mass) x v (velocity)

Impulse (change of P) = F (average Force) x t (change in time)

One of the key things you need to understand about momentum is the Law of Conservation of Momentum (in isolated system, momentum will we be conserved). For example, an apparatus (see picture below) is a prime example of an isolated system where momentum is conserved. Through collision when you hit one ball from one side of the apparatus, the ball on the opposing side of the apparatus is the one that moves. But you also have to notice that none of the other balls in the middle move when the initial ball is moved, only the ball on the opposing end. This demonstrates that the momentum is distributed through all the balls and it's actually pretty cool to watch. 

Momentum: Now what about situations where momentum is not in a conserved, isolated area such as the apparatus? Would the objects go all over the place in a chaotic fashion? Depending on their mass and velocity, maybe. 

In the picture above we can see a great example of momentum and how it is distributed among these pool balls. By apply enough force onto the Que. ball, and by hitting the pyramid of balls, breaking the balls is not a hard thing to do. But notice how the balls distribute, the point of breaking the balls in the first place is to distribute them across the table. This is achieved through momentum. Now how exactly does this happen? Well as described in the definition above, momentum is the strength or force that something has when it is moving or accelerating and when that strength or force is applied with the Que. ball it causes the balls to move. Here ends the reading. 

Forces that Accelerate

Forces That Accelerate

Did you know that according to Newton's Third Law; for every action, there is an equal and opposite reaction and for every force there is an equal and opposite force? Therefore, every time you hit something that thing is hitting you with an equal and opposite force BUT notice that when you hit things that have a significantly smaller mass than you do, that thing is obliterated, so how exactly are the forces the same if the object you hit was no more after you hit it? The answer is simple, the reason the object you hit was obliterated is because it was hit the the same force that you hit it, unfortunately the mass of the object you hit was a lot smaller than your mass AKA māke i ka mea!!!!!!

The picture above is a perfect example of forces that accelerate, although you cant really tell, the cup on the table IS ACCELERATING! It is accelerating down into the table thus putting force on the table, BUT according to Newton's Third Law, the table is supporting the cup with an equal and opposite force pushing on the cup now making it a BALANCED FORCE. We call this balanced force, the Normal force and this theory applies to any objects on a surface. 

 

Newton's First Law Inertia

Newton's first law is inertia. Now, what is inertia? Well, according to Newton's First Law, an object at rest tends to stay at rest unless acted upon by an outside, unbalanced force. For example, if there is an object resting on a table top and there is a sheet of paper pulled out from under it, the object will stay in the position it is in unless unbalanced forced is applied to it. The picture above is a prime example of this, the checker sitting on top of the wooden hoop fell straight into the jar. Now why is that? Well, because there was no force being exerted onto the checker piece, it fell into the jar when the hoop was moved. If you had used the hoop to make the checker unbalanced then it probably wouldn't go into the jar.

Projectile Motion

            In the video below, we can see an example of projectile motion; the motion of the tennis ball when it leaves the hands of Joie (left) and the distance it traveled it hit the ground. The shape of the ball as it falls toward the ground is called parabolic motion. Now although you cant really see how high Joie is off the ground, she is standing on a tall chair that makes her about 6 feet off the ground and she threw the ball with an initial speed of 0.2 meters per second. How would we use math to determine where on the ground the ball landed?

Well, by using physics we can determine where the ball landed without actually measuring how far away from Joie it landed. But before we know far away it landed we have to figure out how long it was in the air. By using the d=1/2at^2 formula we can determine the time, then we would go on to use the d=vt formula to find the distance and it is as simple as that!

Relative Motion

Relative Motion is motion as observed from or referred to some material system constituting a frame of reference. So pretty much it's the idea that motion is all relative. Relative to me the moon follows me in the car at night, but relative to the car, the moon does not move at all.

The picture above is an example of relative motion. The two girls in the back (myself and my friend) are moving out to sea relative to the shore. The reason is because the shore doesn't move at all, but the water does. Relative to the water we're not really moving, but because the shore is stationary we are moving farther and farther away from the shore. Relative to us, the shore appears to be moving because we are moving out to sea when really it is stationary. Everyone on the beach is moving relative to us because we are moving along with the current, where in fact they are stationary as well. 

Projectile motion

If you don't know what the picture above is you clearly have not played the addictive game called angry birds. The point of this game is to knock down the structure ahead using small birds and a sling shot. In order to knock the structure down you have to know what angle to aim the bird so that when it makes it's parabolic acceleration toward the structure it will hit the right point. The parabolic acceleration that the bird is making is an example of projectile motion. Because no matter what the bird will fall in the shape of a parabola due to gravity.

Projectiles

What is a projectile? Well by definition of google, a projectile is any object projected into space with the exertion of force. Would you say that the image of above is a depiction of a projectile yes. Why? Because of the fact that the object was projected into space with the exertion of force. Now you might ask why the object is making a parabolic shape after being thrown before hitting the girl with x's for eyes. Well the answer is simple, gravity. One of the main ideas that makes a projectile a projectile is the fact that the only force on the object after leaving the initial force is gravity itself which will always cause it to go down. Thus the saying, "what goes up must come down."

Letter and Picture Introduction

Letter & Picture Introduction: 

My name is Hayley Kaimalie Cheyney Kane, I am 16 years old and I am a Junior at Kamehameha Schools Kapalama. I am from Kaneohe and Palolo, I live in Kaneohe with my mother and Palolo with my father. Before I came to Kamehameha I attended St. Ann's Model Schools in Kaneohe from Pre-K all the way until the 6th grade. My progresses in science thus far include concepts in biology my freshman year, regular chemistry my sophomore year and honors physics my junior year to keep the flow going but I realized catching up in an honors physics class after missing a week and a half of school results in an F. So I decided to switch regular to make my life that much easier. I am currently in algebra 2B and am thinking of going straight to trigonometry after algebra 2B to help me with my physics. By the end of this course, I hope to achieve a better understanding of what physics is and how it pertains to the world and why we've been taught such different things throughout our lives. 

The picture above is of me at the Miss America's Outstanding Teen Pageant, competing for the title of Miss America OT with my talent which was hula. Although it sounds corny for the Miss Hawaii's OT to be dancing hula for her talent, for me it was a way for me to wow the judges with my culture and personality through dance. I have been dancing hula for about 13 years now and I would definitely say it is my passion. I always marveled in the idea that I could share my thoughts, feelings and emotions through a dance, and it would be something everyone would understand and appreciate. I am the most comfortable when I am dancing hula because of the fact that it's just me being me.