electromagnetic spectrum

  The electromagnetic spectrum is what scientists call the group of different types of radiation.  The waves in the spectrum are commmonly constructed from the longest and lowest in frequency, to the shortest and highest in frequency.  Radiation is energy that emits waves or particles.  Waves in the electromagnetic spectrum do not have to travel through a medium, instead, they are able to traverse through vacuums.

  All electromagnetic waves have four things in common: amplitude (intensity/brightness), wavelength (a length from crest to crest or trough to trough), velocity (speed), and frequency (number of waves per unit in time).  Waves in the spectrum are all transverse waves.

  The seven waves in the electromagnetic spectrum (in order from longest to shortest wavelength) are radio waves, microwaves, infrared waves, visible waves (light), ultraviolet waves, x-rays, and gamma-rays.

RADIO WAVES:

  Radio waves, which have the longest wavelengths in the electromagnetic spectrum, can vary in size from a football to much larger than earth.  Radio waves are primarily used for transmitting signals over a very long distance (more commonly known as long-distance communication).  By bouncing signals off of the ionosphere (layer in earth's atmostphere than contains electron-stripped atoms), the radio waves that are reflected can relay a signal over a huge distance.  However, interference is a common occurence when using radio waves.  Radio waves can travel through most materials, but the wave often slows down, decreasing the quality of the signal.  When the wave gets to a point where it is slowed down a significant amount, interference (static sound) is often heard.  Radio waves are also naturally emitted by things such as stars and gases found in space.

          wavelength = 8 x 10^6 - 3 x 10^0 m

          frequency   = 6 x 10^2 - 1 x 10^8 Hz

  Radio waves are used in our everyday lives to transfer information over a distance without the use of wires.  Listening to the radio, making a phone call, and watching television would not be possible if it weren't for the existence of radio waves.  The images and sound are bounced off of a broadcasting tower and reflected back to us, which allows to watch or listen to the signal by use of the transmission of signals in the form of radio waves.  Radio waves are also heavily relied upon to determine location electronically.  When sent out, they bounce off objects, and reflect back to their origin.  The navy utilizes this phenomenon through the use of radar.  When searching for another ship, radar radio waves are sent out in all directions, and when they come in contact with another ship, they relay the location back to the navy ship, revealing the other ship's exact location.



waves being transmitted



VISIBLE (LIGHT) WAVES:

  The portion of electromagnetic radiation that the human eye can detect (the smallest portion on the spectrum) is referred to as light.  When visible waves are emitted, the retina in a human (or animal's) eye receives and deciphers the light.  The light waves cause a chemical change in our retina, allowing us to see, while light waves that strike materials often cause temperature and electrical changes.  Only visible waves can be received by the retina because other waves in the spectrum have wavelengths either too big or too small.  When light travels through the prism of the retina, the wavelengths seperate into their distinct color of the rainbow (determined by size).  Light waves can be created by an object getting substantially heated, or having a specific chemical or electrical reaction.  Light is able to pass through many materials, such as glass. 

          wavelength = 4 x 10^-7 - 1.5 x 10^-7 m

          frequency   = 4 x 10^14 Hz - 7.5 x 10^14 Hz

  Visible waves are needed for a human to function in everyday life.  Without them, we would not be able to see anything.  Over time, our retinas have developed in order to tune in to certain wave frequences (visible waves) caused by the light emitted from the sun.  Visible waves are also used to make CDs and DVDs.  Microscopic pits are carved into the disc, and when light from the CD/DVD reader is reflected upon the surface, the pattern is deciphered into sound, images, or data.



retina receiving light of the stop sign



bibliography:

pictures:

 http://www.nasa.gov/images/content/201940main_SOMD_Radar_xltn.jpg

https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh5PWM8wIAZtQS9ekc4vxmwdJTcGI5iR6ff48PM64X8ObtwE2JblGO_-LGA7I_U8nCQoBLpNK47fGW83s2dav9reHgsxvfZ-SLXUXdG3ow8RO883keA10t2WRtL3vvB2s1mimAiWWFuU6Q/s1600/retina.gif

information:

http://missionscience.nasa.gov/ems/05_radiowaves.html

http://school.discoveryeducation.com/lessonplans/interact/electromagneticspectrum.html

http://imagine.gsfc.nasa.gov/docs/science/know_l1/emspectrum.html

http://panasonic.net/pcc/support/tel/cdl_noise.htm

http://www.darvill.clara.net/emag/emagvis.htm

http://missionscience.nasa.gov/ems/09_visiblelight.html

http://school.discoveryeducation.com/lessonplans/interact/electromagneticspectrum.html

Conservation of Energy

     Understanding conservation of energy was much easier than I originally thought.  If a person knows the simple rule that initial energy = final energy, then they can pretty much understand any energy problem.  In my example below, an archery business wants to make the best bow and arrow set in the business, but doesn't know what spring constant to use in their bow in order for their arrow to fly at 34 m/s.  The comic explains how to go from a simple equation like initial energy = final energy, to finding a specific variable, for example, the spring constant.

My system (I didn't have enough panels to put in in the pixton):

ATTRIBUTIONS: none (I created all of the characters)

Circular Motion & Gravitation

This is what I learned about circulation motion and gravitation.


circular motion - I have learned that uniform circular motion occurs when an object moves around the circumference of a circle at a constant (doesn't speed up or slow down) speed.  The equation to find the speed of an object in uniform circular motion is v=2πr/T. Even though the variable 'v' is used for the speed, I quickly learned that in this case the 'v' is strictly for determining the SPEED of an object, not the VELOCITY.  An object in uniform circular motion is constantly changing direction, therefore the velocity never stays the same.  The word we were taught to use to describe an object in  (uniform) circular motion is tangential.  The speed is measured in accordance to the vector that is tangential to the circle at that moment in time.


Some general facts and equations we learned about circular motion:
-the period (variable used in equations is 'T') is the time needed to complete on full rotation (or revolution) - and the units is uniformly seconds.  
-the equation for the period 'T' ---> T = 1/f (seconds).


-the frequency (variable used in equations is 'f ') is the number of rotations (or revolutions) per unit in time - the units for frequency are called Hertz (abbreviated Hz).
-the equation for 'f ' ---> f = 1/T (Hertz).


Centripetal acceleration is always found in object moving on a circular path because whenever an object changes direction (which is constantly happening in the case of traveling around the circumference of a circle), acceleration is required.  Centripetal means toward the center, so the acceleration is always pointing towards the center of the circle.  The equation we used to find the centripetal acceleration is Ac=v^2/r.  


Centripetal force, different from centripetal acceleration, is required for any object to move in a circle.  The centripetal force is the actual force that keeps the object being pulled towards the center, keeping it moving in a circle.  Some common examples of forces that can act as centripetal forces are friction, tension, and even gravity.  The equation to find the centripetal force actual comes from Newton's second law, F=ma.  When we substitue the centripetal acceleration, we get Fc=(mv^2)/r.


motion in a vertical circle -  Motion in a vertical circle still has uniform circular motion, but just at a 90 degree (or 270 degree) angle. To solve problems involving motion in a vertical circle, we use the sum of the forces combined with the new formulas concerning circular motion/circular forces.  


universal gravitation - We learned that Newton discovered that a gravitational force, similar to the one between all objects and the earth's surface, exists between any two objects.  Newton stated that the gravitational force varies inversely with the square of the distance between two objects, A.K.A the 'inverse square law'.


The Law of Universal Gravitation says that every object attracts every other object in the universe with a force that varies directly with the product of their masses, and inversely with the square of the distance between the two masses' centers.  The equation for this is Fg=Gm1m2/(r^2).  


I had to pay careful attention to this equation, because there are two different 'g's being used here.  We have first the lowercase g that we are all familiar with, representing the pretty-much-constant acceleration due to gravity on the earth's surface (9.8 m/s^2) - due to the elevation on some areas of the earth's surface - this number can vary because the surface in constantly closer/further away from the sun.  Cavendish determined the value of big 'G' is G=6.67*10^-11 N.m^2/kg^2.


and finally - gravitational acceleration - some objects, such as the earth, we generally know that the gravitational acceleration 9.8 m/s^2.  To find the gravitational acceleration of an object we use the formula mg=GmM/r^2 - the 'm's, or masses, cancel out, so we end up with the simplified equation of g=GM/r^2.  Again, you have to be careful not to confuse the lowercase g with the uppercase G.


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What I have found difficult about this unit  is mainly the conceptual idea regarding how when an object moves in circular motion it is actually being attracted towards the center of the circle.  I understand that a force like friction, tension, or gravity has to be applied to keep the object moving in a circle, but I don't understand how that force (example: friction) is always pointing toward the center of the circle.  In my head, I imagine that the friction force just keeps changing direction according to the tangential motion of the object.  For example, when an object is moving around a circle, the force of friction keeps changing a little bit at a time, in a circular motion - so that the object, in turn, also moves in a circle.  I know that the above statement is wrong, but I don't really understand why/how the friction can point towards the center of the circle.  


Also, I don't really understand what pi is used for/why we use it in our equations regarding circles.


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My problem solving skills have improved GREATLY by studying this unit.  At the beginning of the unit, I was so lost and confused about the concepts of centripetal acceleration/centripetal force, it was just overwhelming.  I think it was because all of the concepts we had previously studied I had somehow previously picked up information about/known a little about the unit coming into it.  Starting this unit, I had a blank slate that was expected to fill up very quickly.  After a couple of classes being completely lost, I   reread the notes at the beginning of each section (which in previous units I hadn't really studied except for some quick skimming), which turned out to help me immensely.  


By doing this I learned that I had to make an effort to understand things that were confusing to me, and not just sit back and wait have things explained to me - because the rest of the class was moving on.  I think I learned this unit that achievement comes with effort, which hopefully shows when I get my test grade back.


Strengths - My strengths in this unit, I think, were my connections I made (more effortlessly than before) about how different concepts connect to each other.  For example, the forces we had just learned about (like friction, tension, etc.) were the same forces that caused centripetal force.


Weaknesses - I think my weaknesses in this unit were mostly all related to problems involving scientific notation.  I'm still not very confident in how to multiply/divide scientific notation, but that turned out to be a small problem because we were allowed to use calculators on every problem.  Still, I think I should be able to do those problems by hand.


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Overall, this unit presented new concepts to me that I hadn't already known about before, and as a result, improved my problem solving skills.

MYTHBUSTERS LAB

  For this lab, we had to disprove two commonly accepted myths. If you asked most people if they thought the myths we were presented were true or not, most people would believe that they were.  Even at first, our lab group had trouble disagreeing with these simple misconceptions.  After a while, we discovered that both myths were actually false in many situations.  

Myth 1: An object always moves in the direction of the net force exerted on it.

If an object always moves in the direction of the net force exerted on it, and we roll a bowling ball across a level carpet surface with friction acting against the ball, then the bowling ball will continue to move in the same direction that it was originally travelling in.

Our procedure for myth one was simple: Roll the bowling ball across the carpet surface.

The small arrow represents the direction of motion.

ΣFx = -Ff

ΣFy= Fn-Fg

The ball is not moving in the way the only horizontal force, friction, is being applied to it.  It still moves to the right, when the force of friction is moving to the left, so the myth is busted!

Myth 2: An object always changes its motion if there is a force exerted on it by other objects.

If an object always changes its motion if there is a force exerted on it by other objects and we swing a tennis ball into a bowling ball while in motion, the bowling ball's path/direction it is going in will not be affected.

Procedure:

1.   Suspend tennis ball from the ceiling with a piece of string.

2.  Hold tennis ball in air while still attached to string.

3.  Roll bowling ball into tennis ball's path.

4.  Release tennis ball from hand, allowing it to swing directly into the bowling ball while it is moving.

 

The small arrow represents direction of motion.

ΣFx = -Fa

ΣFy = Fn-Fg

The ball is moving to the right, but the only force (the applied force of the tennis ball) is moving to the left.  Even though the bowling ball has a left force pushing on it, it is not strong enough to change the direction of the already moving bowling ball (going to the right).  Busted!

CONCLUSION:

We ended up disproving both myths.  But even if we hadn't disproved both, the myth still wouldn't have been proven because we wouldn't have tried every experiment/lab possible.  People believe myth one is true because most people assume the object being forced upon is starting at rest.  For example, a ball at rest gets hit by a foot.  The ball resultantly moves in the same direction as the foot was when it hit the ball.  Most people don't even consider or think about smaller forces like friction.  Because the bowling ball already had enough speed/momentum, the friction acting in the opposite direction did not have any effect on the bowling ball's direction.  People usually believe myth two is correct because they automatically assume the opposing force is stronger than the original object, which is not true in many cases.  For example, in our experiment, the tennis ball had much less force than the moving bowling ball, so the bowling ball's path was not affected at all by the strike of the tennis ball.  Both myths were BUSTED!!!

Physics Carol - On the 12 Days of Physics

On the first day of physics, Mrs. Gende gave to me:
a factor label method for converting units
On the second day of physics, Mrs. Gende gave to me:
one-dimensional kinematics
and a factor label method for converting units.
On the third day of physics, Mrs. Gende gave to me:
constant velocity graphs
one-dimensional kinematics
and a factor label method for converting units
On the fourth day of physics Mrs. Gende gave to me:
distance and displacement,
constant velocity graphs
one-dimensional kinematics
and a factor label method for converting units
On the fifth day of physics, Mrs. Gende gave to me:
acceleration
distance and displacement
constant velocity graphs
one-dimensional kinematics
and a factor label method for converting units
On the sixth day of physics, Mrs. Gende gave to me:
acceleration due to gravity
acceleration
distance and displacement
constant velocity graphs
one-dimensional kinematics
and a factor label method for converting units
On the seventh day of physics, Mrs. Gende gave to me:
SOH CAH TOA
acceleration due to gravity
acceleration
distance and displacement
constant velocity graphs
one-dimensional kinematics
and a factor label method for converting units
On the eighth day of physics, Mrs. Gende gave to me:
vector components and addition,
SOH CAH TOA
acceleration due to gravity
acceleration
distance and displacement
constant velocity graphs
one-dimensional kinematics
and a factor label method for converting units
On the ninth day of physics, Mrs. Gende gave to me:
projectile motion
vector components and addition
SOH CAH TOA
acceleration due to gravity
acceleration
distance and displacement
constant velocity graphs
one-dimensional kinematics
and a factor label method for converting units
On the tenth day of physics, Mrs. Gende gave to me:
free body diagrams
projectile motion
vector components and addition
SOH CAH TOA
acceleration due to gravity
acceleration
distance and displacement
constant velocity graphs
one-dimensional kinematics
and a factor label method for converting units
On the eleventh day of physics, Mrs. Gende gave to me:
Newton's three laws
free body diagrams
projectile motion
vector components and addition
SOH CAH TOA
acceleration due to gravity
acceleration
distance and displacement
constant velocity graphs
one-dimensional kinematics
and a factor label method for converting units
On the twelfth day of physics, Mrs. Gende gave to me:
OUR FINAL EXAMMMMMM!

Erika and Nicole's physics carol.

Newton's Laws of Motion

   Newton's laws have helped me understand the overall concepts of physics, and more specifically, motion, much better.  I have learned that:


Newton's 1st Law - Newton's first law states three basic ideas.
1.  An object that is not moving will not start to randomly move.  It stays at rest.
2.  If an object is moving, and there is not a constantly applied force, the object will continue to move at a constant speed.  However, if another force like friction is applied to the object, it will eventually slow down and come to a halt.  This is true in most cases.
3.  An object in motion will continue in the same direction unless acted upon by another force.  For example, if I am holding a rock in my hand and am moving my arm in big circles, whenever I decide to let go of the rock, it will continue to move in the direction that my arm and hand were last moving in.


Inertia is the resistance each object contains to not change it's state of motion at that moment in time.


I also now understand that the mass of an object is the same anywhere it goes, but the gravitational force (more commonly known as weight) can be different depending on where the object is in the universe.  For example, a 10 kg object is 10kg on earth, and on the moon, as well.  However, that same object will weigh 98 N on earth, but only 16 N on the moon.  This is because the gravitational pull on the earth is more than that on the moon.


I am now also very good at problems involving translational equilibrium, which is when the vector sum of forces upon one object add up to zero.  The object in translational equilibrium is not being moved in any direction because all of the forces cancel each other out.


Newton's 2nd Law - Newton's second law says that an object's acceleration is directly proportionate to the net force, and inversely proportional to the mass of that object.  For me, an example that helps me understand this law a lot better is if I am pushing a block across a horizontal table causing it to accelerate, and then proceed to push that block three times harder - the block will now accelerate three times faster.  The inversely proportional part of the law, using that same situation, means that if the block doubled in mass; the acceleration would consequently be half of the original acceleration.


Newton's 3rd Law - I have learned that Newton's third law basically means each action (or force) has an equal an opposite reaction.  For example, if I were to punch a wall: my fist would be exerting, for example, 800 N of applied force on the wall, and as a result, the wall would also be applying 800 N of force on my fist.  If we did not have this law, simple things like sitting down on a chair would be impossible.  The force of our body on the chair would not have a reaction force of the chair pushing up on our body, so we would simply fall through the chair.  


The last things I have learned are that apparent weight is the amount of force a body exerts on a surface it rests on, and mu helps find the amount of frictional force on an object, which is the opposing force of motion when an object is sliding, sitting still, or even rolling.


What I have found most difficult  in this unit is applying mu concepts to inclined planes.  On problem number 5 on homework 14, an object is sliding down a 30 degree angled ramp with no friction...I can not figure out how to find the mass, so in result I can't seem to find the acceleration, either.  I do not fully understand how to integrate vectors with aspects like friction on an object.  Also, I am sort of confused on what exactly mu is.  I don't really understand how it can have no units, and just be a number...What does the number represent?


I have studied mostly everything in this unit, but the concepts I have spent the most time on are pulley systems and how to approach problems involving a ramp (angle).  I have also spent a lot of time studying how to come up with equations and approach seemingly-difficult problems one step at a time.


My problem-solving skills have become much better due to studying this unit.  I think my ability to follow through each step of a difficult problem has gotten to the point where it comes way more naturally to me than it did before.  For example, I was working on homework #15, which talks about net forces and tensions, when I suddenly realized that everything I was doing, the steps I was taking, the equations, the relationships between the parts in the problem - everything was all very logical.    I think in the beginning of the year I struggled to understand the broad concepts and just focused on understanding the details; when now, I realize understanding what exactly you are doing and the general objective aids me much more than the small details when I go about solving a problem.  Still, I struggle most when first starting out an a problem.  It often takes me a while to think about what I am looking for, and make a plan in my head on how I will solve to get the final solution.


Overall, studying Newton's laws has been a very interesting unit and has greatly improved some of my key problem-solving skills.

Vectors and Projectile Motion

This is what I have learned about vectors and projectile motion:

  1.  Vectors are used to demonstrate the direction and magnitude of an object.  Say a ball is    being pulled in one direction at a certain magnitude, and the opposite direction at a different magnitude.  Which way will the ball actually go and at what speed?  Solving vectors answers this question.  

  2.  Projectile motion is when an object is launched without it's own motive power.  Projectiles always have a constant horizontal velocity, and a vertical velocity that changes throughout the time due to gravity.  An example of this would be a bullet fired from a gun at a 0 degree angle.  How far does the bullet travel?  Where exactly is the bullet at any given time?  What is it's final velocity?  Projectile motion equations aim to answer these questions.

  3.  Projectile motion at an angle is the same as projectile motion, but with an angle (theta) factored in.  A common occurrence of this is shooting a basketball.  Projectile motion is very helpful for solving everyday problems.  

What I have found difficult about what we studied is when I need to resolve the overall velocity into the separate x and y velocities.  But most of all, knowing where and when to apply the correct formula was the most frustrating to me.  There were so many that I couldn't keep track of them all at once.

My problem solving skills have GREATLY improved not only from studying vectors and projectile motion, but from physics class in general.  When I look back at my past work in the assignment and class notebooks, everything prior to these complex problems seems so simple.  Now, instead of focusing on the individual small parts of a problem, I try to look at the big picture first and see exactly what I need to do.  Although I feel much more confident when solving difficult problems, I still have a little trouble knowing where to start/what to do first.  However, I find that every time we start to learn a new concept, I think it will be so hard; but once I understand the overall goal of the unit, the steps start to come easier to me, and suddenly the problems from last unit that I thought were so hard now seem extremely easy.  

Projectile motion and vectors are definitely a part of every day life.  I bet that I see so many examples of these things everyday, but just don't realize it because they are so common.  For example, today at basketball practice I was shooting free throws - I seemed to keep on getting the right horizontal distance, but the vertical velocity being too small caused the ball to keep on hitting the front edge of the rim.  Thinking back, I automatically adjusted my vertical velocity by pushing upward on the basketball with more force than before without even realizing it.  This is a perfect example of projectile motion.

Vectors and projectile motion can be applied to many situations in everyday circumstances.