| Part I: Laws of Motion | The 3 fundamental laws of physics as formulated by Sir Isaac Newton |
| Law of Inertia | inertia - property of a body gives it a tendency to resist change. can also refer to the
actual tendency to resist change na mismo. the amount of inertia an object has is measured by its
mass. pag mas massive ung object/tao, it's harder to get the object moving if at rest, and to stop it
if in motion. kya nga sa x-men si juggernaut pag tumatakbo un di mo mapipigilan kahit steel panels na
ung iharang mo, sobrang massive kac nya Basically the Law of Inertia states that an object will remain in its constant state unless acted on by an outside force. Pag nakalagay lang ang chair dyan, di yan gagalaw magisa. Kelangan me tumulak. Pag ung bola gumugulong, di titigil magisa un, kelangan me pumigil. |
| Law of Acceleration | acceleration - rate of change in velocity. how much bumilis o bumagal ang isang bagay in a
certain time The Law of Acceleration states that if the resultant force or the sum of all the forces applied on a body is not zero, it will accelerate in the direction of the resultant force. Ibig sabihin di pantay pantay ung tumutulak sa object na un. |
| Law of Interaction | Basically, for every force applied on an object there's another force equal in magnitude but opposite in direction that is applied on that object. For example pag nakatayo ka, ung force of weight mo is applied to the floor. At the same time, the floor exerts a force equal to your weight on you. yung opposite forces that are being described here act on different objects, un na nga standing, you exert a force on the floor and the floor exerts force on you. |
| Part II: Waves | A wave is a disturbance travelling thru a medium in a recurring pattern. Wave motion is described as the transfer of energy from one place to another in mechanically propagated waves without the transfer of matter. The medium is displaced and the molecules are moved but they stay in the medium and only the energy of the wave moves. |
| Types of waves | There are two types of waves accdg to how they travel in the medium: Longitudinal - they displace the molecules of the medium in the same direction that they travel Transverse - the medium is displaced perpendicular to the direction of the wave An example of a longitudinal wave is a sound wave travelling through air. It pushes the air molecules together and as it moves forward the air along its path alternates between more dense and less dense. An example of a transverse wave is a water wave, tulad ng "ripples in a pond"... un ... Anyway, ung wave travels horizontally (along the surface of the water) pero the water molecules are displaced vertically (kaya tumataas at bumababa ung water level pag dumaan ung wave). A seismic disturbance creates both transverse and longitudinal waves travelling at different speeds and following different paths kaya pag may earthquake merong vertical shaking and horizontal sliding tas sobrang gulo. |
| Properties | Naalala nyo pa ba ung lesson sa trig last yr? ung sin wave and cos wave (ung me max-0-min etc).. un
ay example ng wave. If i remember correctly me mga properties ung sin wave na meron sa lahat ng
waves: Condensation - when the molecules of the medium are at maximum density and pressure Rarefaction - when the molecules of the medium are at lowest density and pressure Amplitude - the intensity or height of a wave Crest - the highest point in the amplitude Trough - the lowest point in the amplitude Cycle - a complete wave, has all the properties of the whole wave Period - the time it takes for the wave to complete a cycle in phase - when two points are along the same amplitude and going the same direction Wavelength - distance between two points that are in phase (eg. crest to crest) Frequency - the number of cycles completed in a certain amount of time |
| Part III: Sound as a wave | Sound is described as a series of vibrations transmitted through the medium in wave motion. Sound is a longitudinal wave and the sounds we hear are just alternating increases and decreases in air pressure. | |||||||||
| How we hear | Most of the sounds we hear travel through the air. The energy sent out by the vibrations reach our
ears and this energy makes our own eardrums vibrate. The nerves pick up vibrations and our brain
interprets these vibrations as sound. The actual sound we hear is shaped by many factors and properties. Some of these properties affect the loudness and softness, the pitch, or the intensity. Even the quality of the sound differs, and this is how we can perceive the same note played by a different instrument. For example, a high C on a flute sounds different than the same high C on a violin even if they are played with the same loudness. Also, since we were small we've been taught that it's easy to make noise but it's hard to make music. Sometimes it's also hard to get a specific note from an instrument, you end up producing noise. However, in Physics, noise is actually more complex than any pitch because the waveform of noise is a series of peaks and dips which have no harmonic relation. The waveform of a certain pitch is much simpler than the waveform of noise. Contradicting nga eh. |
|||||||||
| Properties of Sound | The properties of a sound wave are the same as any other wave. It also has amplitude and frequency
and these have corresponding effects on the sound produced. A cycle is exactly equal to a single
vibration of the object, meaning that the frequency of a certain sound tells how many times the
object vibrates in one second Frequency which affects the pitch of the sound produced as opposed to Amplitude which affects the loudness and softness of a sound or its volume
|
|||||||||
| Wave disturbance | Actually, these disturbances occur to all waves, not just sound, however inexplain sa atin ang mga
effects in terms of sound that's why it's listed under the sound waves topic. Refraction is the simplest form of disturbance, the most common. It happens when the sound waves are bent from their original path. For example, sound waves moving from warmer to cooler places will be bent by the change in density of the air. Observable effects include poor reception if the sound moves from lower altitude to higher altitude, and better reception/audibility downwind. Sound waves can also be bent by the wind itself, if it's blowing fast enough. Reflection happens when sound waves encounter a barrier and are projected back in a new direction. If the waves hit the barrier perpendicularly the waves travel back but if they hit the barrier at an angle they will bounce at an angle same as that of the angle they hit the barrier with. Isipin nyo bank shot sa bilyar. Sonar depends on bouncing back of sound waves in water. Megaphones make use of reflection to bounce the sounds around and as a result magnify them. Diffraction is the spreading out of waves when they encounter a slit with a size that's close to or even smaller than the wavelength of the wave. This means that if a sound wave passes through a slit, parang nabigyan ito ng new source, parang nagcreate ng new wave from that slit. This explains bakit naririnig parin ang sound sa kabilang room kahit nakasara ung door. Interference is the meeting of two waves which can have either of two effects: to add to each other resulting in a larger wave or to cancel each other producing smaller or no wave at all. The adding is called constructive interference and it happens when two waves meet crest and crest or wavefront and wavefront. The cancellation is called destructive interference and happens when waves meet crest to trough. |
|||||||||
| Part III: Work and Energy | One step after all the force solutions we've been dealing with the whole year |
| Work | Work is defined as a force applied thru a certain distance. If there is no distance moved, then the
resultant work is equal to zero. From the definition, we can get the formula for force to be W = Fd <-- where W is work, F is the force applied and d is the dist. travelled Essentially, if a set-up is in equilibrium, walang work done kahit maraming forces acting on the set up (eg. may nakasabit na bagay: may force of gravity pulling it downward pero may tension of string pulling upward. in this case, walang work done kahit may 2 forces acting, kelangan gumalaw ung setup). Also, kelangan ung motion of the object is caused by the force applied. If it does not move as a result of the force, no work is done (eg. may hawak na tray ung waiter. he exerts force on the tray to hold it up and the tray exerts force of weight to his hand. pag lumakad un papunta sa table, may motion syempre ung tray but it's not caused by the waiter's hand. in this case no work is done on the tray. pero pag tinaas nya ung arm nya at naglift ung tray higher, un may work done na on the tray) If force is measured by Newtons (N or kg·m/s2), then multiplying it by a distance measured in metres will result in a unit of Newton-metres (N·m or kg·m2/s2) this unit is called the Joule (J) and measures energy. Work is simply a term for the energy that was exerted. The other formulae are as follows: 1. for distance travelled d = W ÷ F 2. for force applied F = W ÷ d a Joule divided by a Newton leaves a unit of metres kac ang Joule ay N·m and dividing Joule by meter gives Newtons, so the formula makes sense. |
| Kinetic Energy | Kinetic Energy is energy possessed by a body in motion. Basta't gumagalaw ung object na un meron
cyang KE. Like other forms of energy it is measured in Joules. However, it follows a different formula than Work because you have to take into consideration the mass of the object and how fast it is traveling. [ KE = ½mv2 ] basta't tandaan nyo half of melody times valentine squared un ung kinetic energy Yan ung general formula but if you're looking for another quantity just derive 1. for mass m = 2KE ÷ v2 2. for velocity v = √(2KE ÷ m) We can also conclude that massive objects possess more kinetic energy and so do fast-moving objects. This supports the law of inertia (ung ke juggernaut, ung sa x-men). |
| Potential Energy | If Kinetic Energy is energy that is 'in motion' edi ang Potential Energy is the stored energy that
is possessed by objects at rest. Ikaw pag nakaupo ka lang meron kang stored energy in the form of
food and nutrients (stored chemical energy), chemical energy rin ang tawag sa energy ng battery. Pero
sa term na to, ang tinackle natin na potential energy ay ang energy due to elevation from the ground
(gravitational potential energy) and energy due to elastic tension (elastic potential energy). 1. Gravitational (GPE) - from a height, once it starts to fall, the GPE is turned into KE, this KE is equal to the PE that was stored from that height. Syempre pag nahulog ka, gravity exerts a force on you and you accelerate as you move downward. 2. Elastic (EPE) - elastic materials are those which tend to return to their original state of tension. Pag nistretch mo ang elastic item, pipilitin nya bumalik sa unstretched state. Also, pag kinompress mo, pipilitin nya bumalik sa uncompressed state. Pag nakastretch or compress, meron stored energy which enables it to do work. Here are the formulae for Potential Energy: [ GPE = mgh ] where m is mass and h is height, g is acceleration due to gravity (equal to 9.8m/s2) [ EPE = ½kx2 ] where k is toughness of the elastic item and x is the length it is stretched or compressed **note na ung gravitational potential energy equal lang sya dun sa weight ng object times the height from da ground. tyka ung sa EPE, ung length ay ung how much nastretch or compress, di ung actual length nung mismong string. so if u want to get x, and ur given (kunwari 10cm na spring compressed so that it's now only 3cm) u have to get the diff of the original length and the new (stretched or compressed) length (7cm) un na ung x mo. |
| Power | Power is a quantity measuring how much energy is used/exerted per unit of time. sa definition, we
can say that the formula for power is: [ P = W ÷ t ] ung Power ay equal sa Work (w) divided by time. now if ang work ay measured in Joule (J or kg·m2/s2) at dinivide mo pa uli sa isang unit of time (s) edi ang magiging resulta neto ay kg·m2/s3 and this unit is called the Watt (W) derive the other formulae: 1. for work W = P ÷ t 2. for time t = P ÷ W **note: di ba paulit ulit lang ung mga formula, it's just a matter of what u were given sa problem na pinapasolve syo. marami formula for work, pero kung given syo ung power eto gagamitin mo, kung mass naman kelangan mo muna kunin weight tapos tyka mo gamitin ung any of the other energy or work na formula, un nga depende rin sa kung ano ung given. bakit medyo mali na ang gamitin mong unit for power (sa electric bill) ay ang kW·hr? > kac ang kW·hr, once you convert it to proper units, pde rin maging W·s, and if ang isang watt ay equal sa J/s tapos minultiply mo pa sa s edi nagcancel lang ung dalawang s at balik ka nanaman sa J. so in essence, ang kW·hr ay isang unit for energy, and not power pero sige, tanggapin nalang un |
| Part IV: Problem Solving | In problem solving, sometimes energy chagnes nature. If for example a person jumps from a roof, the GPE he had at the top becomes KE as he starts moving downward. We'll look at how these are applied to the formulae and how to solve correctly. | |||||||||||||||||||||||||||||||||
| Questions and solution | Parang ung reviewer last term, i'll place questions tyka wat formula to use tapos kyo na bahala
magcompute
|
|||||||||||||||||||||||||||||||||