Tuesday, January 25, 2011

ENERGY, ἐνέργεια, Энергия, 能源, Energi (in whatever language you want), it's in Everyday Life

       Energy is a conserved quantity that can change.  It can be transfered from one method to another and also stored in many other ways but it always remains the same amount.  There is elastic, gravitational, kinetic, and potential energy.  Work can be imputed to show the change in the net force as well.  Energy is not just used in physics textbooks, but in everyday life, such as.........   ROCKETS!!!!!  

Helpful Hint: on the glogster the text is large so it is easier to read, that means less space so in every text box you have to scroll.

Rockets Energy Glogster

Picture taken from blog "Les Blog more Art!'

Sunday, January 16, 2011

Universal Gravitaion and UCM or other words, gravity and things that go in circles


Definition - The motion of an object in a circle with a constant or uniform speed.

       Uniform circular motion does not have a constant velocity (due to direction change) and an ever-changing acceleration.  This acceleration due to the centripetal force. (centripetal means inward force that is applied to an object to keep it moving in circular motion, or towards the center.)  Circular motion depends directly on centripetal force and the centripetal force requirement depends on the force that keeps the object in a circlet.  The net force of centripetal force depends on the acceleration, and velocity as well. 


Definition (or the law of universal gravitation) - "every object in the universe 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 centers of the two masses"

       The universal gravitation is the numeric value of 6.67x10^ -11 N.m^2/kg^2.  This figure is most commonly used in the equation Fg= (Gm1m2)/r^2


I have learned that there is an equation to find the gravity of other planets or imaginary places, but that I already at least new a little about.  The thing I learned that was the most 'enlightening' was learning about circular motion.  I did not know that uniform circular motion was always accelerating and I did not know that it did not have a constant velocity.  It does not have a constant velocity because although the magnitude is constant, the direction is always changing.  As our book tells me, this word that describes it is tangential.  Also with uniform circular motion there is period T, frequency, and acceleration.


What I have found difficult is remembering what equations to use, also I have trouble 'improvising' with things such as coefficient of friction but now, after studying for the test, I now understand what to do.  I also used to have trouble with ratios but not anymore (since I studied for the test.)


My problem solving skills have needed improving, I lacked some of the connecting to improvise and impute other equations when needed.  But since studying for the test, I feel like I have improved and understand more of what is really going on in these equations.  Some of my strengths are being able to solve with no problems when I have the equations.  An example is the ratios problem on page 106 in the blue notebook.  It asks to find the value of g if earth's mass was double but the radius remained the same.    I couldn't think of the equation to use.  It didn't occur to me to use the equation that Mrs. Gende gave me because I thought I needed to make a ratio problem.  I made a equation that worked for all the problems and some others that needed to be worked on the notes.  Later Mrs. Gende told me that it wasn't a good equation to use.  And to only use the equation g=GM/r^2.  But in this equation with G is equal to 9.8m/s (with mass as well so mass is canceled out) and when multiplying the other side of the equation is is 9.8m/s,.  The other problem was 43 on page 105.  And I used my equation that I made to solve this problem....  But after speaking to Mrs. Gende I tried that other equation and it worked as well, I was just trying to solve a problem and so I did what I could to solve it.

Tuesday, January 4, 2011

Mythbusters Lab


           This Mythbusters episode is focusing on two myths today.  Each has one experiment, one regular video with an explanation and a cooler video that doesn't explain everything but is fun to watch anyway.

Also; the small, unnamed arrow means the direction in which the ball is traveling.

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

If the object always moves  in the direction of the net force and a basketball is thrown in one direction, then it will keep going in that direction.

Video (plain)

This FBD shows projectile motion, the ball is simply thrown forward.

The ball now moves back toward the person that threw it but the net force shows that it should still be going down.

          As seen in the FBDs the ball continued forward like normal projectile motion but when it hit the ground, according to the 'myth' it should have stopped.  But it moved back up forward with the net force in a downward direction.  This theory is not always true and therefore disproved.  BUSTED!
         Most people believe this myth because it is usually true.  Most of the times it is not then most people regard it as another force acting on it that they don't understand.  It also gives a rational reason for why things are the way they are and people will put their trust in something that is mostly true if there isn't anything that can be all true.

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

If an object always changes in motion if there is a force exerted on it by other objects then a ball rolling toward a container should change direction when it hits it.

Video (plain)

This is the FBD of the ball after it has left the foot so no other applied force is acting upon the ball.  

As can be seen, the direction of the ball didn't change even though another force is acting upon it.

The ball didn't change direction even though it hit the container.  The second FBD disproves the myth by showing that even though other forces were exerted on it it did not change direction to conform to those that force.

          The ball did not change its motion even when another force acted upon it.  Even though it was a small force, it still did not change therefore disproving the theory.  The before equation is BUSTED!
          This myth is believed anyway, even though it can be disproved, because, usually it is true and it also deepens, if a person gets really specific on angle, a very small force can change the direction of the object.  This myth explains many things in our world and it is much simpler to believe in what is mostly true and try to apply it to all.(at least all relating to the subject)

Awesome video to myth #1;

Awesome video to myth #2;