Torque

The calculator can stay balanced on the edge of the table.  It can stay balanced not because there are equal masses on both sides of the edge (fulcrum), but because the torques are the same.  Torque = Force x lever arm distance.  When the torques cancel each other out, the object is at rotational equilibrium.  This can either mean the object is at rest or the object is rotating at a constant speed.

The mass of the calculator lies solely on the center of mass.  If the center of mass is not supported by the fulcrum, then the distance between the center of mass and the fulcrum is the lever arm distance.  

Many things in every day life uses torques.  Turning the knob to open a door uses a torque and so does turning the steering wheel in a car.  

Force

Force is a wonderful thing. It keeps objects, like my sister from falling over.  The formula for force is mass x acceleration.  As seen --> my sister is leaning against the wall without falling.  My sister is pushing against the wall, but the wall is pushing back against my sister keeping her at equilibrium.  Only when the force of my sister is greater than the force of the wall will she move.  

This is Newton's Second Law.  It keeps most objects at rest, either sitting on top a table or or standing on the ground.  The force/push the object exerts on the table/ground is equaled out by the force/push the table/ground exerts back (which can be called the normal force).  It is exerted perpendicularly.  

Evaluation

Physics feels like a whole new language for me.  I thought chemistry was hard enough but physics is completely different.  Its nothing like biology, which is easy for me to comprehend and understand the processes of.  I feel lost in every direction, not knowing where to go like the cartoon man.  I was honestly trying my hardest in the beginning of the quarter to understand the concepts of physics, but it only led to more confusion.  Even after concepts were completed, I didn't feel like I understood anything more than I did before.  

I think I started slacking off in physics after the second test because I felt discouraged by my grades.  Instead of trying to understand better and study more, I used that time to study for other subjects, like biology, even though I'm doing extremely well in that class.  I intend to put way more effort into this class next quarter.  I want to understand and feel accomplished when I get a good grade in physics.  

Inertia

Today my friends and I went to play pool.  While we were playing, I realized that physics played a huge role in the game.  Inertia is the tendency to resist changes in velocity.  It basically means that all objects want to keep doing what they're doing, whether its staying at rest or moving.  Newton's 1st Law of Motion is the Law of Inertia.

The white cue ball is at rest on the table because two equal forces are acting on it.  The weight of the cue ball (mass times gravity) is the downward force and the normal force from the table is the upward force.  Because the upward and downward forces cancel each other out, the net force is zero (equilibrium).  

After the cue ball is hit, it is now in motion.  The weight of the cue ball is still cancelled by the normal force from the table.  Because of inertia, the ball will want to continue rolling at a constant velocity, but because the table has friction, it will eventually stop.

Sound and Wavelengths

I never realized that playing an instrument could have so much to do with physics before.  While playing the piano, fingers hit different notes producing different sounds.  When my sister presses a key on the piano, a pedal connected to the key pounds a string in the back, creating sound waves.  The sound waves are produced by compression and decompression in the air.  The region of compressed air is called a condensation and the region of decompressed air is a rarefaction.  The distance between two maximum condensations or two minimum rarefactions is called a wavelength.  If she strikes a low note, the sound waves produced have longer wavelengths.  If she hits a high note, the sound waves produced have shorter wavelengths.  When a sound wave reaches our ear, the wave causes the eardrum to vibrate.  We technically don't "hear" anything, but we pick up vibrations that our brain interprets into sounds.  

Negative Velocity

Velocity can be either positive or negative, but just because something has a negative velocity doesn't mean that the object is moving slower than something with a positive velocity.  Velocity deals with speed and well as direction.  There is always a positive direction as well as a negative direction, which pairs up respectively with a positive and negative velocity.

During softball, the pitcher releases the ball in the positive direction at a certain speed.  This will have a positive velocity because it is traveling forward.  After the ball makes contact with the bat, it travels in the negative direction with a certain speed.  This speed may be faster or slower than the original speed the pitcher pitched the ball at, but it will always have a negative velocity because it travels backwards.  If, for example, the ball came towards the batter with a velocity of +85 mph and left the bat with a velocity of -90 mph, the ball has a greater speed with the negative velocity, just in the opposite direction.