ADV PHY Reviewer 2nd Quarter PDF

LEGAZPI CITY SCIENCE HIGHSCHOOL 9-CURIE ADVANCE PHYSICS Mrs. Analyn Fernandez NEWTON’S LAW OF the masses. The constant G will remain the same for any two objects anywhere in the U...

LEGAZPI CITY SCIENCE HIGHSCHOOL 9-CURIE ADVANCE PHYSICS Mrs. Analyn Fernandez NEWTON’S LAW OF the masses. The constant G will remain the same for any two objects anywhere in the Universe. UNIVERSAL GRAVITATION G = 6.67x 10^-11 Nm^2/kg^2 TORSION BALANCE EXPERIMENT WHAT MAKES US FALL ON THE EARTH ALWAYS? There is always some force acting on us that Henry Cavendish’s experiment determined the guides our direction of falling. proportionality constant G in 1798. No matter from wherever we jump, or drop objects from anywhere they will always fall towards the earth. WHAT MAKES THE APPLE ALWAYS FALL ON THE EARTH? It was Isaac Newton who posed this question and answered it. Newton stated that all objects attract each other along the line joining their centers. ISAAC NEWTON 1666, England (45 years after Kepler). USES OF GRAVITATION THE UNIVERSAL LAW OF GRAVITATION It is the gravitational force that keeps everything Every object in the universe in its place. Otherwise, we would have been attracts every other object floating in the air. towards itself It also keeps the Earth, sun, and other celestial This force with which the bodies in their right places two objects attract each other It is responsible for many natural phenomena on is called the force of gravitation the earth like tides and orbiting of the moon The force of gravitation acts even if nothing is around the earth. connecting the two objects. Newton did not stop after proposing that a force of gravitation exists. He expressed the law in a KEPLER’S LAWS OF clear and precise language- the language of mathematics. PLANETARY MOTION TYCO BRAHE THE UNIVERSAL LAW OF GRAVITATION STATES THAT.. Danish astronomer Tyco Brahe (1546-1601) had an island Any two point particles with masses m1 and m2 observatory and the best attract each other by a force whose magnitude is measurements of the directly proportional to the product of the two positions for all known planets masses, that is m1m2 and inversely proportional (Mercury, Venus, Mars, Jupiter, to the square of the distance R between them. and Saturn) and the Moon. The direction of the force is along the line joining the two masses. JOHANNES KEPLER Austrian mathematician Johannes Kepler (1571-1630), interested in how the planets move around the sun, went to Tyco’s island to get these accurate measurements. G is a gravitational constant. It does not depend on the value of masses or the distance between LEGAZPI CITY SCIENCE HIGHSCHOOL 9-CURIE ADVANCE PHYSICS Mrs. Analyn Fernandez WHAT IS AN ELIPSE? THIRD LAW An ellipse is a geometric shape with 2 foci The square of the orbital period of a planet is instead of 1 central focus, as in a circle. The sun is directly proportional to the cube of the average at one focus with nothing at the other focus. distance of the planet from the sun. 2 3 T 1 = KR 1 K = 2.97 x 10-19 s2/m3 The farther a planet is from the focus, the longer the period of revolution. VERTICAL CIRCLES Constant speed and direction of object. Gravity either speeds up or slows down objects. LAWS OF PLANETARY MOTION TOP OF THE CIRCLE formula for calculating the tension in the string at the top FIRST LAW of the circle Planets move in elliptical Forces T and mg are downwards. orbits with the sun at one NET FORCE must act towards the center of the of the foci circle. Centripetal force is the sum of two real forces. Kepler also found that Fc should not be labeled in the free body Mars changed speed as it diagram. orbited around the sun: faster when closer to the formula for calculating the minimum or critical velocity sun, slower when farther needed for the block to just be able to pass through the from the sun. But areas A top of the circle and B, swept out by a line from the sun to Mars, were equal over the same amount of time. CRITICAL VELOCITY velocity below which an object moving in a SECOND LAW vertical circle will not describe a circular path. A line from the sun to a Critical velocity depends on the acceleration due planet sweeps out equal areas to gravity and the radius of the vertical circle, in equal lengths of time. not on the mass of the object. A planet will move through an equal area of space in an BOTTOM OF THE CIRCLE equal amount of time formula for calculating the tension in the string at the bottom of the circle Closer to the sun, the faster the velocity because Positive direction towards the center. of the gravitational pull. Net Force acting towards the center: resultant force or difference between T and mg. Notice that the tension in the string is GREATEST as the block passes through the bottom of the circle and LEAST while it passes through the top of the circle. LEGAZPI CITY SCIENCE HIGHSCHOOL 9-CURIE ADVANCE PHYSICS Mrs. Analyn Fernandez Linear velocity of a point depends on: Formula for calculating the tension at any intermediate ★ The rotational velocity of the point. point in a pendulum’s swing More rotational velocity means more linear velocity. ★ The distance from the point to the axis of rotation. More distance from the axis formula for calculating the normal force on the top of means more linear velocity. the circle v = rɷ r = v/ɷ ɷ = v/r ACCELERATION formula for calculating the normal force on the bottom As an object moves around a circle, its direction of the circle of motion is constantly changing. Therefore its velocity is changing. The object moving in a circle is constantly accelerating. FERRIS WHEEL Top: N= mg - (mv^2/r) CENTRIPETAL ACCELERATION Bottom: N = (mv^2/r) + mg The acceleration of an object moving in a circle points toward the center of the circle. CONICAL PENDULUM This is called a centripetal (center pointing) acceleration. g ⋅ tanθ = v^2/r The centripetal acceleration depends on: ★ The speed of the object. UNIFORM CIRCULAR MOTION ★ The radius of the circle. The point or line that is the center of the circle is the axis of rotation. If the axis of rotation is inside the object, the object is rotating (spinning). If the axis of rotation is outside the object, the object is revolving. LINEAR/TANGENTIAL VELOCITY CENTRIPETAL FORCE Objects moving in a circle still have a linear velocity = distance/time. Newton’s Second Law says that if an object is This is often called tangential velocity, since the accelerating, there must be a net force on it. direction of the linear velocity is tangent to the For an object moving in a circle, this is called the circle. centripetal force. The centripetal force points toward the center ROTATIONAL/ANGULAR VELOCITY of the circle. In order to make an object revolve about an axis, Objects moving in a circle also have a rotational the net force on the object must pull it toward or angular velocity, which is the rate angular the center of the circle. position changes. This force is called a centripetal (center-seeking) Rotational velocity is measured in force. degrees/second, rotations/minute (rpm), etc. Centripetal force on an object depends on: Common symbol, ɷ (Greek letter omega) ★ The object’s mass - more mass means Rotational velocity = change in angle/time more force. ★ The object’s speed - more speed means ROTATIONAL & LINEAR VELOCITY more force. If an object is rotating: ★ The object’s distance from the axis ★ All points on the object have the same (radius). rotational (angular) velocity. ★ All points on the object do not have the same linear (tangential) velocity. LEGAZPI CITY SCIENCE HIGHSCHOOL 9-CURIE ADVANCE PHYSICS Mrs. Analyn Fernandez If linear velocity is held CONSERVATIVE FORCES constant, more distance requires less force. A force is conservative if the work it does on an If rotational velocity is held object moving between two points is constant, more distance independent of the path the objects take requires more force. between the points. The work depends only upon the initial and final positions of the object Any conservative force can have a potential energy function associated with it Work done by gravity Work done by spring force CENTRIFUGAL FORCE NONCONSERVATIVE FORCES Centrifugal force” is a fictitious force - it is not an interaction between 2 objects, and therefore A force is nonconservative if the work it does on not a real force. an object depends on the path taken by the Nothing pulls an object away from the center of object between its final and starting points. the circle. The work depends upon the movement path The term "centrifugal force" is often For a non-conservative force, potential energy misattributed to an object's inertia, which refers can NOT be defined to its desire to maintain its desired velocity. It is generally dissipative. The dispersal of energy takes the form of heat or sound Work done by a nonconservative force BANKED CURVES A banked curve is a curve that has its surface at an angle with respect to the ground on which the curve is positioned. The reason for banking curves is to decrease the ENERGY moving object's reliance on the force of friction. ABILITY TO DO WORK v = √rgtanθ As you know, energy comes in many forms. ❖ Kinetic Energy kulang to may notes nmn kayo ng formula bala kayo ❖ Potential Energy diyan ❖ Gravitational Potential Energy (gravity) ❖ Elastic Potential Energy (springs, rubber WORK AND ENERGY bands) ❖ Chemical Energy (chemical bonds) TYPES OF FORCES ❖ Rest Mass Energy = Nuclear (E = mc2) ❖ Electric Potential Energy (ΔU = kq1q2/r) ❖ Thermal Energy (heat = KE of molecules) CONSERVATIVE FORCES ❖ Sound (waves) Work and energy associated with the force can ❖ Light (waves/photons) be recovered ❖ Examples: Gravity, Spring Force, EM forces LAW OF CONSERVATION OF ENERGY NONCONSERVATIVE FORCES The forces are generally dissipative, and work “Energy can neither be created nor destroyed. It done against it cannot easily be recovered can only be converted from one form of energy to ❖ Examples: Kinetic friction, air drag another. ” forces, normal forces, tension forces, applied forces LEGAZPI CITY SCIENCE HIGHSCHOOL 9-CURIE ADVANCE PHYSICS Mrs. Analyn Fernandez CONSERVED QUANTITIES the change in the Kinetic Energy of the body. Other conserved quantities that you may or may not already be familiar with? Conservation of mass. Conservation of momentum. POWER Conservation of charge. the rate at which work is done CONSERVED OF ENERGY unit of power is watt (W) 1 W is energy transferred at the rate of one joule The Law of Conservation of Energy simply states per second that: P = w/t ❖ The energy of a system is constant. 1 000 w = 1kilowatt ❖ Energy cannot be created nor 1 hp = 750 watt destroyed. P = energy transformed/ time taken ❖ Energy can only change form (e.g. electrical to kinetic to potential, etc). ❖ True for any system with no external forces. ❖ ET = KE + PE + Q (Constant) ❖ KE = Kinetic Energy ❖ PE = Potential Energy ❖ Q = Internal Energy [kinetic energy due to the motion of molecules (translational, rotational, vibrational)] KINETIC ENERGY P = w/t T = w/P W = Pt energy of motion the energy an object possesses due to its motion. The faster an object moves and the more massive it is, the greater its kinetic energy. KE = ½ mv^2 v=√2KE/m POTENTIAL ENERGY the stored energy an object has due to its position or state. energy of position The two common types are gravitational potential energy and elastic potential energy. PE = mgh MECHANICAL ENERGY the sum of an object's kinetic energy and potential energy. In the absence of non-conservative forces like friction, the total mechanical energy of a system remains constant. WORK-ENERGY THEOREM The Work-Energy Theorem explains that the net work done by all the forces acting on it is equal to