Physics

Thuong Thai, Mark Do, Milan Patel, Michael Nguyen, Ramses

Carranza

Scientific Method

• It is the process by which science moves forward

• Hypothesis- educated guess• First step is to address the problem, it can be

used without an experiment.

SI Units

• Length= meters• Mass= Kilograms• Time= Seconds• Mega = 10^6• Kilo= 10^3• Deci= 10^-1• Milli= 10^-3• Micro= 10^-6

Basic Conversions

• 2.54Cm = 1 in• 3ft= 1 yd• 5280 ft= 1mi• 1609m = 1 mile• 14.59 kg= 1 Slug• 2.2 lb = 1 kg• 231 cubic inches= 1 gallon

Scalars and Vectors

• Scalars= Magnitude only• Vectors= Magnitude and Direction• Ex of Scalars: Temperature, time, speed.• Ex of Vectors: Velocity, force, Momentum

Kinematics

• Description of Motion• Position is distance from origin• Displacement: Amount your distance changed

over time.• Velocity: Displacement/ Time• Speed= Absolute Value of Velocity• Acceleration: Velocity/ Time

Kinematics Equations

• v= initial velocity+(a)(t)• Displacement= (.5)(Initial v+ Final v)(t)• Displacement= Initial v*t + .5(a)(t)^2• V^2= (intial V)^2 + 2(a)(Displacement)

Galileo & Newton

• Objects fall at the same rate. Free Fall Acceleration is 9.80 m/s^2 (32 ft/ s^2)

• Influence of Gravity points down towards the core.• Newton Wrote the Philosophiae Naturalis Principia

Mathematica.• 1st Law: An object at rest will tend to stay at rest

unless acted upon by an external force.• 2nd Law: F=ma• 3rd Law: Every Force has an equal or opposite force.

(Forces measured in N)

Projectile Motion

• Any object that has motion in both vertical and horizontal direction and falls solely under the retarded influence of gravity while in the air.

Forces and Friction

• Normal Force: Contact Force the arises when two objects are impress against each other.

• Friction: Two objects rub against each other • Static Friction: Attempts to keep things

stationary• Kinetic Friction: Tries to slow down motion.

Energy

• Quantity that an object possess and is related to its ability to do something. It cannot be created or destroyed.

• Kinetic Energy: Energy in motion.• Potential Energy: Stored Energy• KE= (.5)(m)(v)^2• PE= mgh

Conservation of Energy

• The total energy of a system will not change but the values of the types of energy may change within the system.

• Initial energy = Final Energy• Initial KE+ Initial PE= Final KE+ Final PE•

Momentum

• Impulse is a vector quantity (J)• J= F(time interval)• Momentum (p)= mv (vector)• Impulse = change in momentum• Collision: Elastic Collision (Conservation of

energy and momentum) • Inelastic Collision (Conservation of momentum

but not energy.)

Simple Harmonic Motion (SHM)

• Periodic motion that arises from a restoring force such as a pendulum.

• Distance from peak to equilibrium = Amplitude (A)

• Period (T) How long it takes to repeat motion (s)

• Frequency: How often the object passes by a certain point. (1/T)

Section 2:WavesI. Traveling WavesTraveling wave- a fluctuation traveling in some type of matter, AKA medium. They deliver energy from one location to another.Medium- substance that tends to return to equilibrium when displaced(can be solid, liquid or gas).Amplitude- distance from the peak or trough to equilibrium. When it's positive-peak, when it's negative-trough.

Traveling waves(continued)Wavelength- distance for a wave to repeat its motion.

Measured from peak to peak or from trough on displacement vs position graph.

Period- how long it takes a point at a fixed location on a wave to repeat it's motion. To find it on a displacement vs

time graph, measure from peak to peak or trough to trough. Measured in seconds.

Frequency- how often a certain wave displacement such as a peak, passes by an observer at a fixed

location. It’s the inverse of the period. Unit is Hz or cycles per second

Wave velocity -found by multiplying the wavelength and frequency. Represents speed at which the wave is

propagating through the medium.

Traveling waves(continued)

The wavelength depends on the frequency and wave velocity. The frequency depends on the wave source. The wave velocity depends on the medium

Transverse Waves

For a transverse wave, the displacement of the wave medium is perpendicular (think 90 degrees) to the direction of travel of the wave.

Light- a true transverse wave. Transverse vibrations of electric charges create light waves. Frequency of light visible to us is between 4x10^14Hz and 7x10^14Hz. In air, light waves correspond to wavelengths of 700nm(red light) and 400nm(violet light). Human eyes are most sensitive to light with a wavelength of 560nm(yellow-green light).

Transverse waves(continued)

Light waves- wave that can go through a medium but can also go through a vacuum. The wave speed of light in a vacuum is 3.0x10^8 m/s(c). From a vacuum to any medium, light will slow down.

The index of refraction, n, relates how much slower something travels in a given medium compared to how it moves in a vacuum. Equation--> n=c/v . the index of refraction (in a medium) is a unitless ration and has to be greater than one

Longitudinal wavesLongitudinal wave- a wave where the displacement

takes place in the same direction. Physically, they are a compression of particles that propagates through the medium.

Sound- an example of these waves. It is a fluctuation of density or pressure in a given medium. The more the particles in the medium interact, the faster the wave speed. The speed of sound is 340 m/s. The speed of sound in water is about 1,100 m/s.

Humans can hear sounds between 20Hz and 20,000Hz. Sounds under 20Hz-infrasonic. Sounds above 20,000Hz-ultrasonic

Wave interference

Superposition- addition of the amplitudes of the two waves(AKA wave interference).Constructive inteference- when two waves overlap such that their peaks are at the same position so their amplitudes combine as a result.Destructive interference- when two waves overlap such that the peak of one wave is at the same position as the trough of the other wave at the same time so that the amplitudes combine to make an amplitude of zero.

Reflection and Refraction

Reflection is where light bounces off an object.

Refraction is where light bends and fires into a different direction.

Snell’s law states that n1sin(theta1)=n2sin(theta2). Theta1 stands for the angle of incidence and theta2 stands for the angle of refraction. n1 stands for the index of reflection and n2 stands for the index of refraction.

Types of Lenses

A converging lens focuses parallel light rays, while diverging lenses defocus parallel light rays. Light rays come together at what is called a focal point.

Electricity and Magnetism

The SI unit for electrical charge is q, which is Coulombs, or C.

Charge cannot exist without an object.

Positive and negative charges attract and the same charges are repulsive, or repel.

Robert Millikan developed the idea that each charge is a fundamental unit of a smaller charge.

The charge for an amount of charge is 1.602 *10^-19 Coulombs.

Electricty/Mag. Cont’d

Charles-Augustin de Coulomb was the first person the quantify force between two or more electrical charges. The electrical force is equal to + (electrical constant)(multiply the 2 electrical charges/center-to-center distance^2).

• The electrical constant k(e) is 8.99 * 10^9 Nm^2/C^2.

• This formula is Coulomb’s Law.

Electrical Fields

Electrical Fields are represented by E.

The equation for it is the source charge*electrical field.

The electrical field due to a charged point particle will be the Electrical Field = kq/distance squared.

Conductors are materials that allow electrons to move freely.

Insulators are objects that oppose the movement of electrons.

Rearranging electrons present within an object is knows as Induction of Charge.

Electrical Potential Energy is V, measured in Volts.

Cont’d

Electrical potential energy(PE elec)= k (product of the two electrical charges/distance).

PE elec is a scalar quantity and has the SI Unit Joules(J).

Voltage = PE elec/electrical charges (scalar quantity as volts)

Capacitance refers to an object’s ability to hold a stationary charge. C=the electrical charge/change in voltage

A capacitor is a device that is designated to store energy in the form of an electrical field.

C=(permittivity of free space) * Area/distance

Permittivity of free space(E0)=8.85*10^-12 N/m^2.

Energy= .5C(change in Velocity^2)

Currents

Electrical Current, I, is the amount of electrical charge that passes by a specific point in a certain time period. I=change in q/time interval.

Ohm’s Law states that the change in voltage=IR(or electrical current*resistance)

Also, P=I(delta V), P being electrical power.

Other forms of the equation are: P=RI^2 and P=(delta V^2)/R.

Batteries are represented by 2 parallel lines.

A cursive E stands for emf(ElectroMotive Force).

Equivalent resistance is to take complicated circuits and break them down.

Resistance

• Kirchoff’s Rule

• First of his rule is the junction rule. It is a statement of conservation ofc charge. It states that the sum iof the currents entering any junction must equal the sum of the currents leaving that junction.

• Second part is the loop rule. This rule is a statement of conversation of energy. The sum of the voltage differences across the elements around any closed circuit must be zero.

Magnetism

Danish physicist and chemist Hans Christian Oersted were the founders of magnetism.

To determine the direction of the magnetic field, you can use the Right Hand Rule 1 (RHR1).If you put your thumb in the direction of current flow while grasping the wire with your right hand, then your fingers curl in the direction of the magnetic field. The magnetic fields will form concentric circles around the wire.

Magnetic Fields vs. Poles

Magnet is similar to electric charges. There are like charges/or poles that repel each other while opposite charges/poles attract each other. However there is a major difference in that we can separate a positive charge from a negative charge, but we cannot separate north poles from south poles