Variable resistors

this weekend i saw 2 instances of variable resistors in the world. a variable resistor is a strip of metal connected to a circuit. This piece of metal can change the overall resistance of the circuit by having its length changed. This change in length determines the amperage of the circuit and thus the ending result. one place i saw this resistor was in my kitchen where we have a dimmer switch. This switch dims the lights by lengthining the resistor. Also another application of variable resistors i saw put to use was in my car. When turning up the volume on my stereo i noticed that the volume switch was also a variable resistor. by turning the nob clockwise i shorten the resistor, thus increasing the output of the circuit. this leads to more charge reaching the speaker, directly resulting in louder sound.

Static Electricity

This Super Bowl weekend was quite hectic and probably had some of the best weather in a while. As a result i decided to wash and wax my car. I applied the wax in a circular motion to the newly washed car. As i rubbed the sponge applicator on the metal surface of the car i noticed an electric field forming around the recently waxed area. i knew that this field existed because i felt the hairs on my arm tingle and attract to the surface of the car. Apparently, the wax used to detail the car is a good insulator and thus holds a charge in a single place rather well. This is because on an insulator, the electrons cannot move aroun very well and thus stay concentrated. The wax on the car demonstrated this property and it became charged by my actions of applying it to the car. By rubbing the wax onto the metal body of the car i removed electrons from the car body and onto the wax. Therefore the wax held the charge and through induction attracted my arm haors which hyappened to be within its electric field.

Boxing Physics

A couple of weeks ago I was watching the Manny Pacquiao fight with Oscar De La Hoya.  I noticed the great impact physics had in the fight.  Pacquiao, the smaller man, was able to cause much more damage with his punches than De La Hoya did with his. Causing damage with a punch is really a simple physics concept.  the concept behind this is the transfer of momentum from the puncher to his opponent. Due to the conservation of momentum,the more momentum the punch has, the more damage inflicted to his opponent.  This would leave one to believe that the only two variables, mass and speed, in determining a punch's power.  If this were true then the bigger man, De La Hoya, would have a significant advantage in the mass department.  But then why so much power from the smaller Pacquiao? To answer that question one must see that it is not only pure velocity but rather the change in velocity that indicates a punch's power.  This increases the force of the blow because it reduces the time the punch is in contact with the opponents face.  This also explains the difference in Pacquiao's and De La Hoya's punching power.  Pacquiao snapped his punches all night making sure they quickly rebounded, while De La Hoya just threw his arms out there hoping to catch his elusive opponent.  This slight difference in punching technique gave Pacquiao a decisive knockout and catapulted him to the status of world's number one pound for pound fighter.

Momentum

recently in physics we have been learning about momentum.  Momentum is  a function of the mass of an object multiplied by its velocity.  Therefore the heavier an object is and the faster it is moving the greater its momentum.  i noticed this the other day wen for conditioning we were throwing medicine balls.  I noticed that the heavier the ball the greater the force of impact was when i caught it.  I  also noticed that the ball when thrown harder had more force.  These conclusions all made sense to me but the lightbulb really clicked wen i noticed that when a lighter ball was thrown faster it had an impulse equal to that of the slower heavier ball.  

Elevators

Today while riding in the elevator i noticed a real world application of an Atwood machine.  Since the lab we did using an atwood machine to "dilute" gravity i have noticed their applications in the real world.  Also i have noticed that elevators put energy into a system and therefore do work.  They do work because when they raise you they increase your gravitational potential energy.  the amount of work they do is equal to the height they raise you, this is then multiplied by the force it take for u to be raised.  the value that then results from this is the amount of work done.  But because an elevator is an atwood machine some of this weight is offset by the counterweights.  

End of 1st Quarter

This Quarter has been pretty fun overall.  I enjoy coming to physics knowing that there are hardly any dull moments in class.  Yet i still have some reservations about the class. I'm still adjusting to this whole online assignment sheet and I'm finding it a bit unnerving because i often forget to check the homework.  Also there are some other issues. I've realized that i must study for tests more diligently  and take special care on the multiple choice part.  I's also finding it rather difficult this year to balance my workload from all my classes and i haven't yet found a successful way to organize my thoughts.  Overall i enjoy most of my teachers this year and i place Physics as one of my favorite classes.

Newton's Second Law

This weekend while i was driving i had a physics epiphany.  I drove two very different cars this weekend, one was my Mom's large white Honda Odyssey van and the other was my Volkswagon Passat sedan.  I noticed that while both cars have engines with almost identical horsepower it takes much longer for the van to reach freeway speeds compared to the sedan.  i found that the reason for this was that the sedan is a much smaller car, thus weighing less.  Due to the formula F=ma the van which has significantly more mass takes more force in order to accelerate at the same rate as the smaller sedan.  This thought struck me as i was driving up the H2 freeway and noticed i had to press on the gas alot harder in the van than in the sedan.