Saturday, February 21, 2009

Chinese food

I was eating at a Chinese restaurant when several spoons flew off of the spinning table in the center. The inward frictional forces of the spoons were less than the required mv^2/r that would have kept the spoons spinning in a circular motion. The spoons therefore traveled in a trajectory off of the table that is tangent to the rim of the table. The mustard, on the other hand, had a larger normal force and frictional constant that allowed the mustard to stay on the spinning table.
In this perfectly drawn picture, the block has a inward frictional force that keeps it on the table. One spoon flies off of the table at tangency since it does not have enough frictional force. A spoon that has a smaller radius is also traveling at a slower linear velocity than the other spoon.

Sunday, February 15, 2009

Relative velocity

I was sitting in the back of a pickup truck while tossing a coin up in the air. At first when I tossed it relatively low, the coin seemed to fall as if I was sitting inside of the truck. It fell straight down in my perspective because it had the same horizontal velocity of the car. To someone on the sidewalk, however, it would look as if it was moving in a parabolic motion. When I threw the coin higher, however, the coin encountered a wind force that slowed down the horizontal motion of the coin. This resulted in the coin landing on the road in back of the tailgate. This drawing illustrates the air flow.
When the tailgate is up, an air pocket is formed. This helps the truck to be more aerodynamic. If the tailgate is down, the air current will have higher pressure above the bed, increasing the drag of the truck in motion.

Sunday, February 8, 2009

Circuits

Physics has shown that when wired in parallel, potential difference does not change among resistors. This would be the ideal way to wire a house because a large potential difference will not be needed. Rather than be shared among resistors in series, resistors in parallel will have the same potential difference as the power source. If potential energy is high, power will increase(P=IV). Parallel is also ideal for wiring a house because if something like a light bulb burns out, the rest of the circuit will continue to work. In series, the entire circuit would not work because the circuit is broken at the bulb. The best example of this are christmas lights. If one bulb breaks, you would have to check each bulb to see which one broke if it is wired in series. Finding out which bulb burnt out would be a pain.

Wednesday, January 21, 2009

Air Pump

According to the regulation bounce of a basketball, when the ball is dropped at the full extension of the arm the ball should bounce to shoulder level. In order to inflate my slightly deflated ball, I needed to do work to move the pump. The work allowed air to be pushed into the ball. Unlike a heat engine where air currents do work, the pump required work and resulted in air change. The volume of the pump is compressed (isobaric) so that air flows out. The ball remained isochoric as the volume never changed.
The ball bounces higher once air is pumped in because the impact with the ground becomes more of an elastic collision with more air in the ball.
By using work to push the handle in, air flows out of the nozzle and into the ball creating more pressure.

Thursday, January 8, 2009

Dr. Ignacio's Presentation

Dr. Ignacio was able to share a little insight to being an orthopedic surgeon. It was interesting to see the situations that required a "carpenter" to fix. Surgery required knowledge of not only biology, but many of the sciences including physics. She was able to convey all of the hard work and schooling needed in order to become a doctor in any field. She is an example of following your passion rather than following what others believe is right. She decided to work in the field of sports medicine and orthopedic surgery despite being outnumbered by many males. It was inspiring to see such a successful Iolani graduate.

Sunday, December 14, 2008

Radio

Physics continues to play a part in everyday life, even while listening to the radio. Transmitters send radio waves at a specific frequency so that our radios can transfer them into sound. This allows the broadcast of many different channels. Listening to the radio also made me think about the differences between the voices of Perry and Price. What makes their voices unique to themselves? The sound waves that are emitted by their voice box contain different frequencies and harmonies. The graph of this sound wave would not be a definite sine function, but a graph of many crests and troughs.
The Mighty Mo contains many radio transmitters so that it can communicate with all military command.

Sunday, December 7, 2008

Speed bump

I was driving in my car when I approached a speed bump. I slowed down and as the car's front two wheels fell, I could feel the frequency of the springs. This meant that physics was at work yet again. As I landed, the car bounced, as if it were in harmonic motion. The weight of the car landing created the force that would make the car no longer exist in equilibrium. This motion, however is not in simple harmonic motion. As shown in this picture, the car's shocks will actually compress a little as it rides up the bump in order to keep the body of the car at a constant level.
Upon landing, the shocks will become stiffer (higher spring constant) so that the car will not bounce. The spring constant of shocks are able to change because of hydraulics and air pressure.