My dad always takes me home from school.  Sometimes, when he really wants to make a light he speeds up and makes a sharp and quick turn and now I'll relate it to physics.  During the sharp turn, I feel pushed to the outside of the turn because of centrifugal force.  Centrifugal force is the fake force that we feel on a turn because inertia gives us the tendency to want to continue going straight.  The magnitude of centrifugal force is equal to that of centripetal force so Fc=m*v^2/r or Fc=m*rω^2.  When the turn is sharp, the radius decreases increasing centripetal force.  When the turn is fast velocity increases and this also increases centripetal force.  Because centripetal force is equal to centrifugal force, the sharper and faster the turn, the more your body will be pushed to the outside.


Some pictures of turns

Physics Blog 6

When I was on the computer last night, I accidentally hit my water bottle down.   The water got on my keyboard and mouse so I went to get a paper towel and absorb the water.  As I was doing this, I noticed that my hand and the water bottle created a sticky collision which moved the water bottle off the table.  Gravity then took control and tipped the bottle over and water spilled out.  Sticky collisions are m1v1+m2v2= (m1+m2)vf so we can find final velocity from our givens.  My hand was moving at around 4.2672 m / s and has a mass of about 1.81436948 kilograms.  The water bottle, which was half full had about 191.722284 grams or .191722284 kilograms. It's initial velocity was 0. Vf= (m1v1+m2v2)/ (m1+m2).  (1.81436948* 4.2672+.191722284*0) /2.00609176= 3.8593835 m/s. 

Physics Blog 5

Last night, I went to sleep at 1:30 because there was a marching band competition that lasted until 12:00.  So, when I woke up at 9:00 today, I was extremely tired (more tired than I usually am on a Sunday Morning).  Because I was so tired, when I walked down the stairs, I fell and went rolled the way down.  When I looked up at the stairs, I realized that gravity had done work on me.  Work equals force times distance and in this case work is equal to mass*gravity*height.  My weight is the force that that was acting upon me and makes gravity * mass while the I fell distance is equal to the height of the stairs.  Although the stairs makes an angle with the horizontal, the amount of work that is done is still the same as if I was just falling from a height of the highest stair.  My stairs are each 18 cm and there are 16 of them so the total height is .18*16m or 2.88 meters.  After I fell all the way down to the bottom floor, I found that Gravity did 55.6*9.8*2.88 joules or 1569 joules of work on me.  I did -1569 Joules of work because I did the same amount of work in the opposite direction.  And then I went back upstairs to sleep.

Yesterday, (October 16, 2010) I watched the the Hawaii VS. Nevada football game.  After watching the play replay of the  Nevada player, Mike Ball, make a 84-yard kickoff return, I noticed that when the first diving tackle missed by a Hawaii player, the player slid about 2 meters before coming to a rest.  This is due to friction.  When the football player dove, he had an initial velocity and was like a projectile.  However, after he hit the ground, he slid across the ground before stopping.  After watching this, I decided to try and the find mu of his jersey to the AstroTurf.  We can find the mu.  Because he was sprinting before he dove, his initial velocity was around 7 m/s.  If he slid 3 meters on the ground then we know his acceleration is- 8.2 m/s^2 because 7^2=2(a)3. If his weight was 200 pounds, then his normal force would also be around 200 pounds.  200 pounds is equal to about 890 newtons and this means his mass is 81.6 (890/9.8 = 81.6 kg).  a=Net Force/ mass.  Net Force = 81.6*-8.2=-670N.  Friction = 670N.  890*mu = 670N and therefore mu is 0.75.

Blog 3

On Friday, October 3 2010, my physics teacher, Mrs. Chen had a substitute by another physics teacher, Doc. For a real life example of the lesson, he made the whole class ride the elevator. As we went up to the third floor from the first, we could feel our bodies getting heavier for the first few seconds. Later during the ride, we felt normal, and finally after that we felt lighter. These changes that we experienced are caused by the change in our normal force. When we are just standing, we have two forces acting upon us: normal force and our weight. Normal force is the force that negates the force of gravity. On the elevator, our normal forces rose and stayed constant for a while before decreasing back to a halt. The normal force affected our net force and our net force changed our acceleration. As we accelerated upwards, our normal force rose making us feel heavier. When the acceleration became 0, our normal force also became 0. When we slowed down before reaching the fourth floor, we felt lighter because our normal force decreased. We also felt this as we went back to the first floor but in the opposite order. The same thing can be said about a scale. When I push down on the scale, the scale reads higher but when I don't push down as much then the scale reads lower. The scale is reading the normal force. I can't fix this font...

 With less normal force.

 With more normal force.

. 

Normal Normal Force.

Blog 2

For XC practice last week, we ran to Kapiolani park to play ultimate Frisbee.  While playing, I noticed that at the tennis courts nearby, the players were hitting the ball with their racket.  I also noticed that the  soccer ball was being kicked by the soccer players on the nearby soccer field.  At this moment, I recalled that when the soccer ball is kicked it is like a vector.  Its horizontal velocity was constant throughout it's flight while its vertical velocity made a parabola.  It had a negative acceleration of 9.8 meter per second squared and its vertical velocity, therefore, was decreasing in speed on the way up and increasing in speed on the way down.  At the top of its altitude, or maximum height, its vertical velocity is 0.  This soccer ball reminded me of a great soccer game between Iolani and Millilani for the state finals which took place last year.

Physics Entry #1: XC Meet

On September 4, 2010, I had a cross country meet at Waipio Soccer Park for Iolani School JV/ Varsity.  During the race, I was running at around 3.5 meters per second (from 22 minutes for 3 miles) but when I got to a steep and long hill, my pace slowed even though I was putting in more effort.  The hill was about a 45 degree angle from the ground and approximately 15 meters long.  I came to the top of the hill in about 25 seconds making my pace slow down to .6 m/s.  My velocity slowed down because I ran fighting the force of gravity which is 9.8 meters per second^2 in the negative direction or to the ground.  My legs became especially sore on this hill.  Other runners also slowed down.  This picture isn't a picture of me but of other intermediate runners on their 2 mile event at Waipio.

My first one

I just created this on 8/29/10 for physics class