Indo Board

Last summer, my cousins and I were playing with Kyle’s Indo board. Every time I tried, I always fell off right away. However, Kyle could keep moving on it for a long time and even do some crazy tricks. The Indo board reminded me of a concept we learned in physics. In order to stay on the board my cousin would have to make sure his center of mass was always supported. The center of mass is the average location of mass. The center of mass has to be supported in order to be balanced or else the object will fall over. The equation for the center of mass is: XCM= (m1x1 + m2x2 +…mnxn) / (m1 + m2 +…mn). Next time I go to my cousin’s house and go on the Indo board again, I have to make sure my center of mass is supported so I do not fall off. Hopefully if I get better, my cousin can teach me some tricks.

swimming POOL

Today, I remembered that last winter my friends and I went to play pool at Hawaiian Brians after a a tough wrestling tournament. Since it was late there was hardly anyone else there. Thinking of this day reminded me of physics and the concept of momentum we are learning about. At first before I hit the cue ball, it has a momentum of 0kgm/s and a velocity of 0m/s. Once i strike the cue ball, the ball will gain momentum and velocity. In a bouncy or elastic collision momentum and kinetic energy is conserved. P1=Pf (initial momentum = final momentum). KE1=KEf (initial kinetic energy = final kinetic energy). Therefore, after the cue ball hits the balls and they all go off in different directions, all of their momentum combined should add up to the momentum of the cue ball when it them. Also, their kinetic energies should add up to the kinetic energy of the cue ball.

i dont like Motorola

Before I started doing homework in my room, I placed my cell phone on the desk. I later noticed that my cell phone on the desk related to physics. My cell phone has potential energy since it is at an elevated position (my desk). Since the cell phone is not moving it has zero kinetic energy. However, if the phone was to move off the desk and fall to the ground, the kinetic energy will increase. Potential energy = mgh which is mass (kg) times gravity (9.8m/s^2) times height (m). Kinetic energy = 1/2mv^2 (v = velocity m/s). Even though the potential energy will change as it falls to the carpet, the total energy (potential energy + kinetic energy) will always remain the same. Hopefully, my dad will let me get a new phone that is not a Motorola. When I had this phone at KMC for senior camp, mine was the only one that had no bars. This phone is always giving me problems. Grr!

last post of the quarter ^__^

Physics has been a fun course so far. I enjoy learning about how physics relates to me and things that happen every day. For example, driving a car, throwing a ball, or seeing objects resting on tables. However, I am very worried. The labs have been fun and interesting, but were difficult. Also, some of the homework assignments have been tough. I have trouble solving most of the problems. T___T I am worried that physics is going to get harder next quarter. I am already struggling with the concepts we are learning in physics now. >__< My goal for next quarter is to raise my quiz and test grades. If I can do this then hopefully I can get a decent grade for this course. That would be awesome. I’m praying very hard that I do well on the upcoming test on Wednesday. The picture above is a picture of my cousin. I don’t know what you think, but I think he looks very worried, which is why I am using it for this journal entry.

Throwing Paper

Today I decided to clean my room, because people where coming to my house. I started by taking the clothes off the ground and putting them away. Then I began to clear my desk from all the empty water bottles and random pieces of paper. I started launching them into the trash can. I realized at that moment that I was making a projectile with the balls of paper I was throwing. The crumpled piece of paper's horizontal velocity remained the same. However, because of the gravity (-9.8m/s²) the ball of paper falls after reaching its maximum height and gains velocity in the negative direction. When the ball of paper reaches its maximum height, its velocity is zero. In order to find the initial velocity, I must measure change in Y or vertical displacement. I also need to find the time it takes for the paper to reach the trash can after it is released from my hand Once I find those values I can plug it into this equation: ▲y=Viyt + 1/2at² to find the initial velocity.

Falling Grapes

This afternoon while sitting at my kitchen table, I was eating some grapes. When I reached into the bowl and grabbed a hand full, one grape slipped through my fingers and rolled off the table and fell to the ground. Watching my grape plummet from the edge of the table it reminded me of physics. It reminded me of gravity and how objects fall at constant acceleration.

The acceleration of the grape falling to the wooden floor was 9.8m/s^2. The displacement would be the distance is rolled on the table and the height of the table. The ending velocity when it hits the ground would b zero. If I were to draw the acceleration graph it would b a horizontal line connected to 9.8 on the y-axis and would run till whatever time the grape hit the ground. I also remembered that even though two objects may be different in weight, they will still fall at the same acceleration.

Playing with my Dog

Earlier today at home, my dog ran up to me with her toy in her mouth. I took the doll from her, tossed it, and watched her go after it. Her action reminded me of something I learned in physics. If I was the origin and tossed the doll, my dog would be running forward with a positive acceleration. When she slows down to grab the doll, her acceleration becomes negative. When she turns around and runs back toward me she has a positive acceleration but a negative velocity. This is because she turns around and is running back toward me, the origin. Once she reaches me and stops, the total displacement is zero because her initial starting spot was where she ended.

So if I was to graph her running, the position graph would look like a short steep slope when she is running toward the doll then a gradual one when she grabs it. Then it would gradually go down then become steep once she picks up speed back toward me. The velocity graph would be a gradual hill going up then drop back to zero once she reaches the doll then it would become a negative slope as she runs back toward me. The acceleration graph would go from zero to positive when she is speeding up toward the doll, then negative to positive when she slows down to grab the doll and then speeds up toward me, and finally negative to zero as she slows down to a stop where I am.