Blog 7 Circular Motion

 Over the summer, my brother competed in the Waimea swim series race.  He and the rest of his swim team had to swim 2.1 km at Waimea Beach.  Although my brother did not win, and he actually got dq'd because he swam around the wrong side of the buoy.....However there is still physics everywhere, even in swimming races!  In this picture you can see swimmers turning to get around the buoy, where the center of rotation is somewhere out of the picture near the beach.  As the swimmers turn, they are moving in a circle, however with such a large radius, an average speed, and all the forces of drag and friction between the water, it is very unlikely that they will surpass their centripetal force and fly off in a tangent!  Although that would be very interesting to see.  As we continue to learn more physics, we realize that there really is physics everywhere and you just have to know what it is.

Blog 6: Momentum

In this video the conservation of momentum is shown because the momentum of the first ball is transferred to the second ball once they collide.  Although the first and the second ball do not have the same kinetic energy (velocity) before and after the collision because energy is lost to friction and sound, the momentum of the of the total system is conserved throughout the collision. The mass of the two balls must be the same or very similar because they are the same size, same manufacturer and same material so mass is irrelevant in this example.  Therefore, the velocity of the first ball right before it hits the second ball must be equal to the velocity of second ball plus the first ball right after the collision because of conservation of momentum.  Physics is everywhere, even at McCully Bike.

Blog 5: Power

Since I fail at computers (I actually had to audit Java programming to not get an E and screw my GPA) I cant embed this video, but its super funny, so click on the link.(And after posting this I realize it doesn't even let you click, so highlight, control-c, or right click copy and open a new tab and watch it!)

http://www.youtube.com/watch?v=182GMMxyuOk

I recommend skipping to 0:53 if you want to laugh.

In this video the boy experiences the power of roller coasters.  While the coaster is going up at the beginning its velocity is very slow, so it does the work very slowly as well, resulting in low power.  This is because Power=work/time, so the longer it takes the roller coaster to reach the top, the lower the power.  After the coaster reaches the top however and it makes its descent down, its velocity becomes very fast, so it does work quickly, increasing its power.  With so much power acting on him, the boy goes insane and yells for no reason.   The lesson here: don't try to answer questions about baseball on roller coasters, otherwise someone will tape you and you will be a laughingstock on youtube.  Power is fun!

Inertia - Blog 3

Like probably everyone else in our class, I'm doing the table cloth dish trick.  Although I wanted to do it with my whole table, my mom was freaking out and would only let me do it with one plate and a table setting.  In the video the plate and fork move very little when I pull the table setting out from underneath them, this is because of the plate and fork's inertia, their resistance to change in velocity.  Since the plate was at rest at the beginning of the video, it will stay at rest unless acted upon by an outside force, this outside force is the setting.  When I pull the table setting out from under the plate it exerts a net force on the plate, but because I move it so fast this net force can only act on the plate for a fraction of a second, not providing enough time to move the plate very far.  If I had instead moved the plate very slowly, it would exert a small net force on the plate for a longer amount of time, thus pulling the plate along with it across the table. 

P.S. I realize that it wasn't very smart to pull the plate and film it by myself, so I apologize for the blurriness when the setting was actually pulled out from underneath, but I assure you, that the plate hardly moved at all!

Blog #2

Sunday afternoon rolls around again, and as usual I have successfully procrastinated the whole weekend, in an attempt to have something to do for this assignment I simply dropped a tennis ball of my balcony, original isn't it?  As all things in free fall, the ball has projectile motion, as it falls down it accelerates at a constant rate of -9.8 m/s^2 due to gravity.  Due to gravity it has increasingly negative y velocity as it falls, but since it had no initial x velocity, when it hits the ground it has the same x velocity, 0.  This is because x velocity is constant throughout projectile motion because gravity only works in the vertical direction, not the horizontal.  For simplicities sake, I said that the ball had a initial x velocity of 0, but in reality because she slightly pushed it off the ledge, it did have a very small amount of initial x velocity, which explains why the ball fell in a parabola shape instead of a straight line, as the x velocity determines how far the object travels.  Well that's all for this week, time to start my homework.

Acceleration in Action

Acceleration in Action.  Making a right turn outside my local 7-11, this white car shows physics in a real world application.  Coming to a stop at the light before he makes his turn, his velocity is 0.0m/s, then turns right and accelerates while getting onto Hawaii Kai Drive.  He needs to accelerate to match the flow of traffic, but can not accelerate too much as Hawaii Kai Drive is notorious for speed traps!  Physics is applied everywhere in the real world, all you have to do is look for it.