General Physics 1 Second Quarter Module PDF

GENERAL PHYSICS 1 SECOND QUARTER Week 1 Torque and Angular Momentum MELC : Calculate magnitude and direction of torque Apply torque-angular momentum relation Determine angular momentum of different system INTRODUCTION Which one of the above application of force, F i...

GENERAL PHYSICS 1 SECOND QUARTER Week 1 Torque and Angular Momentum MELC : Calculate magnitude and direction of torque Apply torque-angular momentum relation Determine angular momentum of different system INTRODUCTION Which one of the above application of force, F is the easiest to open a door? DEVELOPMENT Torque is derived from the Latin word torquere, which means ' to twist'. Torque is the turning force. It is a vector quantity. Unit of measurement is newton · meter (N · m). It is simplest to view the torque as consisting of two pieces. One part that has the same direction as the object's rotation axis, and other part that is at a right angle to the rotation axis. τ = Fl (magnitude force times the moment arm) = rFsinθ where τ is the torque, r is the perpendicular distance, F is the force and θ is the angle between r and F The torque is positive when the force tends to produce a counterclockwise rotation about the axis, and negative when the force tends to produce a clockwise rotation. direction will not make the object's rotation speed up or slow down, however. It will change the spin direction - a phenomenon known as precession.  Consider this : You are installing a new spark plug in your car, and the manual specifies that it be tightened to a torque that has a magnitude of 45 N.m. Using the data in the drawing, determine the magnitude F of the force that you must exert on the wrench. _______________________________________________________________________ _______________________________________________________________________ _______________________________________________________________________ ENGAGEMENT A shop sign weighing 220 N is supported by a uniform 120-N beam as shown below. 1. Draw a free-body diagram for the beam, showing all the forces acting on the beam. 2. Break the tension in the guy wire into horizontal and vertical components. 3. Write down two equations by balancing the forces in x and y directions. 4. Write down the torque equation. 5. Find the tension in the guy wire and the horizontal and vertical forces exerted by the hinge on the beam. ASSIMILATION The first condition necessary to achieve equilibrium is the net external force on the system must be zero. Simply net F =0. Note that if net F is zero, then the net external force in any direction is zero. For example, the net external forces along the typical x- and y-axes are zero. This is written as net Fx = 0 and Fy = 0. The second condition necessary to achieve equilibrium involves avoiding accelerated rotation (maintaining a constant angular velocity). A rotating body or system can be in equilibrium if its rate of rotation is constant and remains unchanged by the forces acting on it. Torque is the turning or twisting effectiveness of a force. It is the rotational equivalent of a force. It is a measure of the effectiveness of a force in changing or accelerating a rotation (changing the angular velocity over a period of time). Now, the second condition necessary to achieve equilibrium is that the net external torque on a system must be zero. An external torque is one that is created by an external force. If the second condition (net external torque on a system is zero) is satisfied for one choice of pivot point, it will also hold true for any other choice of pivot point in or out of the system of interest. (This is true only in an inertial frame of reference.) The second condition necessary to achieve equilibrium is stated in equation form as net τ = 0 where net means total. Torques, which are in opposite directions are assigned opposite signs. A common convention is to call counterclockwise (ccw) torques positive and clockwise (cw) torques negative. Week 2 ROTATIONAL KINEMATICS & MOMENT OF INERTIA MELC : Apply the rotational kinematics relations for systems with constant acceleration Calculate the moment of inertia of a single object and multiple object system INTRODUCTION Investigate how torque causes an object to rotate. Discover the relationships between angular acceleration, moment of inertia, angular momentum and torque. Go to this site if you may -http://cnx.org/content/m42170/1.5/torque_en.jar DEVELOPMENT Why do tornadoes spin at all? And why do tornados spin so rapidly? The answer is that air masses that produce tornadoes are themselves rotating, and when the radii of the air masses decrease, their rate of rotation increases. An ice skater increases her spin in an exactly analogous manner. The skater starts her rotation with outstretched limbs and increases her spin by pulling them in toward her body. The same physics describes the exhilarating spin of a skater and the wrenching force of a tornado. Clearly, force, energy, and power are associated with rotational motion. These and other aspects of rotational motion are covered in this chapter. We shall see that all important aspects of rotational motion either have already been defined for linear motion or have exact analogs in linear motion. First, we look at angular acceleration—the rotational analog of linear acceleration. Angular Acceleration Uniform Circular Motion and Gravitation discussed only uniform circular motion, which is motion in a circle at constant speed and, hence, constant angular velocity. ENGAGEMENT Recall that angular velocity ω was defined as the time rate of change of angle θ : ω = Δθ Δt , where θ is the angle of rotation. The relationship between angular velocity ω and linear velocity v was also defined in Rotation Angle and Angular Velocity as v = rω or ω = vr , where r is the radius of curvature. According to the sign convention, the counter clockwise direction is considered as positive direction and clockwise direction as negative. This figure shows uniform circular motion and some of its defined quantities. Angular velocity is not constant when a skater pulls in her arms, when a child starts up a merry-go-round from rest, or when a computer’s hard disk slows to a halt when switched off. In all these cases, there is an angular acceleration, in which ω changes. The faster the change occurs, the greater the angular acceleration. Angular acceleration α is defined as the rate of change of angular velocity. In equation form, angular acceleration is expressed as follows: (1 α = Δω/Δt ,where Δω is the change in angular velocity and Δt is the change in time. The units of angular acceleration are (rad/s)/s , or rad/s2. If ω increases, then α is positive. If ω decreases, then α is negative. Calculating Angular Acceleration & Deceleration of a Bike Wheel Suppose a teenager puts her bicycle on its back and starts the rear wheel spinning from rest to a final angular velocity of 250 rpm in 5.00 s. (a) Calculate the angular acceleration in rad/s2 (b) If she now slams on the brakes, causing an angular acceleration of – 87.3 rad/s2 , how long does it take the wheel to stop? Strategy for (a) The angular acceleration can be found directly from its definition in α = Δω Δt because the final angular velocity and time are given. We see that Δω is 250 rpm and Δt is 5.00 s. Solution for (a) Entering known formula into the definition of angular acceleration, we get Because Δω is in revolutions per minute (rpm) and we want the standard units of rad/s2 for angular acceleration, we need to convert Δω from rpm to rad/s: Entering this quantity into the expression for α , Strategy for (b) In this part, we know the angular acceleration and the initial angular velocity. We can find the stoppage time by using the definition of angular acceleration and solving for Δt , yielding Solution for (b) Here the angular velocity decreases from 26.2 rad/s (250 rpm) to zero, so that Δω is – 26.2 rad/s , and α is given to be – 87.3 rad/s2 Thus, In circular motion, linear acceleration a , occurs as the magnitude of the velocity changes: a is tangent to the motion. In the context of circular motion, linear acceleration is also called tangential acceleration (at). An object undergoing circular motion experiences centripetal acceleration,. Thus, at and ac are perpendicular and independent of one another. Tangential acceleration at is directly related to the angular acceleration α and is linked to an increase or decrease in the velocity, but not its direction. Moment of Inertia It is a measure of an object’s resistance to changes to its rotation. The total moment of inertia is due to the sum of masses at a distance from the axis of rotation. In short, it is the angular equivalent of mass. And must be specified with respect to a chosen axis of rotation. Unit of measurement = kg.m² The total moment of inertia s due to the sum of the masses at different points from the axis of rotation. It depends on mass and axis of rotation. A rotating mass has kinetic energy. Kinetic energy depends on moment of inertia and angular velocity. ASSESSMENT Thought experiment Imagine yourself playing in a merry go-round with 3 other kids rotating with angular velocity w=3 rad/s. First sitting near the center (r=1 m), in case B they are near the edge (r=3 m). Compare the kinetic energy of the kids on the two rides. KE = 4 x ½ m v2 = 4 x ½ m ωr2 = ½ I ω2 Where I = 4 m r2 Further mass is from axis of rotation, greater KE it has. Activity 1 Grab a PVC pipe and spin it with your hand. Now make 2 rings that will fit the pipe. The rings must have a significant weight that you can move up and down the pipe. Place the rings near the center of the pipe and spin it. Next place the rings near the edges. Did you notice any difference? _____________________________________ ___________________________________________________________________ ___________________________________________________________________ WEEK 3 - 4 NEWTON’S LAW OF UNIVERSAL GRAVITATION & KEPLER’S LAWS OF PLANETARY MOTION MELC : Use Newton’s law of gravitation to infer gravitation force, weight and G Discuss the physical significance of gravitational field Relate Kepler’s laws to Newton’s Law of Gravitation INTRODUCTION Isaac Newton compared the acceleration of the moon to the acceleration of objects on earth. Believing that gravitational forces were responsible for each, Newton was able to draw an important conclusion about the dependence of gravity upon distance. He came up with his Universal Law of Gravitation which states the relationships of mass and distance to Gravitational constant G DEVELOPMENT THE UNIVERSAL GRAVITATION EQUATION Newton's law of universal gravitation is about the universality of gravity. This is due to his discovery that gravitation is universal. ALL objects attract each other with a force of gravitational attraction. Gravity is universal. This force of gravitational attraction is directly dependent upon the masses of both objects and inversely proportional to the square of the distance that separates their centers. Newton's conclusion about the magnitude of gravitational forces is summarized symbolically as Since the gravitational force is directly proportional to the mass of both interacting objects, more massive objects will attract each other with a greater gravitational force. So as the mass of either object increases, the force of gravitational attraction between them also increases. If the mass of one of the objects is doubled, then the force of gravity between them is doubled. If the mass of one of the objects is tripled, then the force of gravity between them is tripled. If the mass of both of the objects is doubled, then the force of gravity between them is quadrupled; and so on. The constant of proportionality (G) is known as the universal gravitation constant = 6.674×10−11 m3⋅kg−1⋅s−2.. The precise value of G was determined experimentally by Henry Cavendish in the century after Newton's death.  Answer this- 1. What happens to the gravitational force between two bodies if one of the masses is increased by a factor of three? What if both masses are increased by a factor of 3? _______________________________ 2. Due to Newton’s Third Law, the gravitational force felt between two objects is equal and opposite. Explain whether a heavier or lighter object would have a greater acceleration towards each other and why. __________________________________________________________ 3. According to Newton’s Universal Law of Gravity, we should feel a force of attraction from all objects around us. Why is it then that we do not feel it? __________________________________________________________ 4. If you double the distance between two objects, how does the gravitational force change? _______________________________________________ 5. If the gravitational force felt between two objects is 20 N, what is the gravitational force if the distance between the two objects is reduced by half? ______________________________________________________ Gravity is very important to our everyday lives. It is the Sun's gravity that keeps the Earth in orbit around the Sun. Life on Earth needs the Sun's light and warmth to survive. Gravity helps the Earth to stay just the right distance from the Sun, so it's not too hot or too cold. Gravitational field affects all masses in its vicinity pulling them towards the center. If the gravity is strong enough then it also affects light. ENGAGEMENT If the object goes where the gravitational field strength is different from the gravitational field strength on Earth, such as into space or another planet such as the moon which is smaller and has less mass than the Earth, he will weigh lighter than on Earth. Johannes Kepler was a German astronomer, mathematician, and astrologer. He is a key figure in the 17th-century scientific revolution, best known for his laws of planetary motion, and his books Astronomia nova, Harmonices Mundi. These works also provided one of the foundations for Newton's theory of universal gravitation. Three laws devised by Johannes Kepler to define the mechanics of planetary motion. The first law states that planets move in an elliptical orbit, with the Sun being one focus of the ellipse. This law identifies that the distance between the Sun and Earth is constantly changing as the Earth goes around its orbit. The second law states that the radius of the vector joining the planet to the Sun sweeps out equal areas in equal times as the planet travels around the ellipse. As such, the planet moves quickest when the vector radius is shortest (closest to the Sun), and moves more slowly when the radius vector is long (furthest from the Sun). Both where published in Astronomia Nova. In this second book Harmonices Mundi, his  states his third law based on the ratio of the squares of the orbital period for two planets is equal to the ratio of the cubes of their mean orbit radius. This indicates that the length of time for a planet to orbit the Sun increases rapidly with the increase of the radius of the planet's orbit. NEWTON & KEPLER Newton's comparison of the acceleration of the moon to the acceleration of objects on earth allowed him to establish that the moon is held in ASSESSMENT a circular orbit by the force of gravity. Newton provided credible evidence that the force of gravity meets the centripetal force requirement for the elliptical motion of planets PROBLEM SOLVING (10 pts) 1. Determine the force of gravitational attraction between the earth (m = 5.98 x 1024 kg) and a 70-kg physics student if the student is standing at sea level, a distance of 6.38 x 106 m from earth's center and when he is standing on top of Mt. Everest. WEEK 5 PERIODIC MOTION AND WAVES MELC : Describe periodic motion and waves Calculate the period and frequency of spring mass Recognize the necessary conditions for an object to undergo simple harmonic motion INTRODUCTION What does a rocking chair, a bouncing ball, a vibrating tuning fork, a swing in motion, the Earth in its orbit around the Sun, and a water wave have in common. They are all examples of periodic motion. , in physics, motion repeated in equal intervals of time. DEVELOPMENT Mechanical Waves Mechanical Waves are waves which propagate through a material medium (solid, liquid, or gas) at a wave speed which depends on the elastic and inertial properties of that medium. There are two basic types of wave motion for mechanical waves: longitudinal waves and transverse waves. Period and Frequency in Oscillations In the absence of friction, the time to complete one oscillation remains constant and is called the period (T). Its units are usually seconds, but may be any convenient unit of time. The word ‘period’ refers to the time for some event whether repetitive or not, but in this chapter, we shall deal primarily in periodic motion, which is by definition repetitive.A concept closely related to period is the frequency of an event. Frequency (f) is defined to be the number of events per unit time. For periodic motion, frequency is the number of oscillations per unit time. The relationship between frequency and period is f=1/T The SI unit for frequency is the hertz (Hz) and is defined as one cycle per second: 1Hz=1cycle/sec A cycle is one complete oscillation. SIMPLE PENDULUM has a small-diameter bob and a string that has a very small mass but is adequate not to stretch significantly. The period of a simple pendulum is given by T = 2π √l/g Where, l = Length of a simple pendulum; g = acceleration due to gravity. From the equation, we can write the relation between the time period of a pendulum and acceleration due to gravity as T is inversely proportional to √g. The time period of the simple pendulum is independent of the amplitude, provided the amplitude is sufficiently small. The time period (T) is constant when effective length (L) and gravity (g) are constants. This means that a pendulum will take same time in completing each oscillation, whatever is the amplitude, provided the latter does not exceed 4o. The time period of the simple pendulum is directly proportional to the square root of its length. So, T ∞ √L, when g is constant. As the expression doesn’t contain the term ‘m’, the time period of the simple pendulum is independent of the mass and material of the bob. Since the time period of a simple pendulum depends on the length and acceleration due to gravity at a given place, it is used to determine the time in clocks that work on the standard of the simple pendulum. It is also used to find out the acceleration due to gravity at a place. SIMPLE HARMONIC MOTION In simple harmonic motion, the acceleration of the system, and therefore the net force, is proportional to the displacement and acts in the opposite direction of the displacement. A good example of SHM is an object with mass m attached to a spring on a frictionless surface. The object oscillates around the equilibrium position, and the net force on the object is equal to the force provided by the spring. This force obeys Hooke’s law Fs=−kx, as discussed in a previous chapter. If the net force can be described by Hooke’s law and there is no damping (slowing down due to friction or other nonconservative forces), then a simple harmonic oscillator oscillates with equal displacement on either side of the equilibrium position, as shown for an object on a spring The maximum displacement from equilibrium is called the amplitude (A). The units for amplitude and displacement are the same but depend on the type of oscillation. For the object on the spring, the units of amplitude and displacement are meters. ASSSSMENT Choose the best answer (2pts) WEEK 6 SOUND MELC: Apply the condition of standing waves on a string Relate the frequency and wavelength of sound with motion of the source and listener Apply the inverse-square law INTRODUCTION Sound waves are incapable of traveling through a vacuum. DEVELOPMENT The relationship of the speed of sound, its frequency, and wavelength is the same as for all waves: vw = fλ, where vw is the speed of sound, f is its frequency, and λ is its wavelength. Sound wave compressions and rarefactions travel up the ear canal and force the eardrum to vibrate. There is a net force on the eardrum, since the sound wave pressures differ from the atmospheric pressure found behind the eardrum. A complicated mechanism converts the vibrations to nerve impulses, which are perceived by the person. As an example, suppose a Bowling ball and Ping-Pong ball have the same velocity, then the Bowling ball will have greater momentum because it is bigger than the Ping-Pong ball. One of the more important properties of sound is that its speed is nearly independent of frequency. This independence is certainly true in open air for sounds in the audible range of 20 to 20,000 Hz. If this independence were not true, you would certainly notice it for music played by a marching band in a football stadium, for example. Suppose that high-frequency sounds traveled faster—then the farther you were from the band, the more the sound from the low-pitch instruments would lag that from the high-pitch ones. But the music from all instruments arrives in cadence independent of distance, and so all frequencies must travel at nearly the same speed. Recall that vw = fλ. In a given medium under fixed conditions, vw is constant, so that there is a relationship between f and λ ; the higher the frequency, the smaller the wavelength. STANDING WAVE The waves move through each other with their disturbances adding as they go by. If the two waves have the same amplitude and wavelength, then they alternate between constructive and destructive interference. The resultant looks like a wave standing in place. Standing waves are also found on the strings of musical instruments and are due to reflections of waves from the ends of the string. Image show three standing waves that can be created on a string that is fixed at both ends. Standing waves on strings have a frequency that is related to the propagation speed vw of the disturbance on the string. The wavelength λ is determined by the distance between the pointswhere the string is fixed in place. NODES-ANTINODES Nodes are the points where the string does not move; more generally, nodes are where the wave disturbance is zero in a standing wave. The fixed ends of strings must be nodes, too, because the string cannot move there. The word antinode is used to denote the location of maximum amplitude in standing waves. Nodes are areas of wave interference where there is no motion. Antinodes are areas of wave interference where the motion is at its maximum point. SONIC BOOM There is constructive interference along the lines shown (a cone in three dimensions) from similar sound waves arriving there simultaneously. This superposition forms a disturbance called a sonic boom, a constructive interference of sound created by an object moving faster than sound. Inside the cone, the interference is mostly destructive, and so the sound intensity there is much less than on the shock wave. An aircraft creates two sonic booms, one from its nose and one from its tail. Sonic booms are one example of a broader phenomenon called bow wakes. A bow wake, is created when the wave source moves faster than the wave propagation speed. Water waves spread out in circles from the point where created, and the bow wake. DOPPLER EFFECT The whistle of a fast moving train appears to increase in pitch as it approaches a stationary observer and it appears to decrease as the train moves away from the observer. This apparent change in frequency was first observed and explained by Doppler in 1845. The phenomenon of the apparent change in the frequency of sound due to the relative motion between the source of the sound and the observer is called the Doppler Effect. USES Doppler shift in ultrasound can be used to measure blood velocity. Police use the Doppler shift in radar (a microwave) to measure car velocities. In meteorology, the Doppler shift is used to track the motion of storm clouds; such “Doppler Radar” can give velocity and direction and rain or snow potential of imposing weather fronts. In astronomy, we can examine the light emitted from distant galaxies and determine their speed relative to ours. As galaxies move away from us, their light is shifted to a lower frequency, and so to a longer wavelength—the so-called red shift. LAW OF INVERSE SQUARE The Inverse Square Law teaches us that for every doubling of the distance from the sound source in a free field situation, the sound intensity will diminish by 6 decibels. The intensity of the sound is inversely proportional to the square of the distance of the wavefront from the signal source. ASSESSMENT Answer the following (2 pts each) WEEK 7 SPECIFIC GRAVITY, PRESSURE AND BUOYANCY MELC : Relate density, mass, volume and specific gravity Apply Pascal’s principle Apply Bernoulli’s Principle Apply Archimedes’ Principle INTRODUCTION Matter most commonly exists as a solid, liquid, or gas; these states are known as the three common phases of matter. Solids have a definite shape and a specific volume, liquids have a definite volume but their shape changes depending on the container in which they are held, and gases have neither a definite shape nor a specific volume as their molecules move to fill the container in which they are held. Liquids and gases are considered to be fluids because they yield to shearing forces, whereas solids resist them. DEVELOPMENT The Density Calculator uses the formula p=m/V, or density (p) is equal to mass (m) divided by volume (V). The calculator can use any two of the values to calculate the third. Density is defined as mass per unit volume. Specific gravity is the density of a material at a certain temperature divided by the density of water at a certain temperature; the reference temperature is usually 20 degrees Celsius. PASCAL’S PRINCIPLE AKA Pascal's law. In fluid (gas or liquid) mechanics, states that, in a fluid at rest in a closed container, a pressure change in one part is transmitted without loss to every portion of the fluid and to the walls of the container. BERNOULLI’S PRINCIPLE In fluid dynamics, Bernoulli's principle states that an increase in the speed of a fluid occurs simultaneously with a decrease in static pressure or a decrease in the fluid's potential energy. The principle is named after Daniel Bernoulli who published it in his book Hydrodynamica in 1738. Bernoulli’s equation considers only pressure and gravitational forces acting on the fluid particles. Therefore, if there is no change in height along a streamline, Bernoulli’s equation becomes a balance between static pressure and velocity. ARCHIMEDES PRINCIPLE States that the buoyant force on an object submerged in a fluid is equal to the weight of the fluid that is displaced by that object. If a glass is filled to the top with water and then ice cubes are added to it, what happens? Just like the water spilled over the edge when Archimedes entered his bathtub, the water in the glass will spill over when ice cubes are added to it. If the water that spilled out were weighed (weight is a downward force), it would equal the upward (buoyant) force on the object. Why the rock sinks? So, in other words, an object will float if it weighs less than the amount of water it displaces. This explains why a rock will sink while a huge boat will float. The rock is heavy, but it displaces only a little water. It sinks because its weight is greater than the weight of the small amount of water it displaces. From the buoyant force, the volume or average density of the object can be determined.  Uses of the Archimedes principle The Archimedes principle is a very useful and versatile tool. It can be useful in measuring the volume of irregular objects, such as gold crowns, as well as explaining the behaviors of any object placed in any fluid. Archimedes' principle describes how ships float, submarines dive, hot air balloons fly, and many others examples. ASSESSMENT WEEK 8 - 9 LAWS OF THERMODYNAMICS MELC : Explain the connection between the Zeroth Law, temperature, thermal equilibrium and temperature scales INTRODUCTION Heat transfer is energy in transit, and it can be used to do work. It can also be converted to any other form of energy. A car engine, for example, burns fuel for heat transfer into a gas. Work is done by the gas as it exerts a force through a distance, converting its energy into a variety of other forms—into the car’s kinetic or gravitational potential energy; into electrical energy to run the spark plugs, radio, and lights; and back into stored energy in the car’s battery. DEVELOPMENT Thermodynamics states that heat is a form of energy, and thermodynamic processes are therefore subject to the principle of conservation of energy. This means that heat energy cannot be created or destroyed. FIRST LAW OF THERMODYNAMICS The first law of thermodynamics, also known as Law of Conservation of Energy, states that energy can neither be created nor destroyed; energy can only be transferred or changed from one form to another. SECOND LAW OF THERMODYNAMICS According to the law, heat always flows from a body at a higher temperature to a body at the lower temperature. This law is applicable to all types of heat engine cycles including Otto, Diesel, etc. for all types of working fluids used in the engines.  THIRD LAW OF THERMODYNAMICS ENGAGEMENT The third law of thermodynamics states that the entropy of a system at absolute zero is a well- defined constant. This is because a system at zero temperature exists in its ground state, so that its entropy is determined only by the degeneracy of the ground state. For example, at close to absolute zero, many materials lose all resistance to the flow of electric current, shifting to a state called superconductivity. ZEROTH LAW OF THERMODYNAMICS states that if two systems are in thermodynamic equilibrium with a third system, the two original systems are in thermal equilibrium with each other For example, consider two separate cups of boiling water. If we place a thermometer into the first cup, it gets warmed up by the water until it reads 100°C. We now say that the thermometer is in thermal equilibrium with the first cup of water. 1. What is the definition of thermodynamics? a) The energy available to do work. b) The study of the relationship between heat, work, and energy. c) The amount of heat it takes to move an engine. d) The movement of heat. 2. What was the name of the prevailing theory of heat prior to thermodynamics? a) Heat Equals Work Theory b) Kinetic Theory c) Caloric Theory d) Heat Power Theory 3. Which of the following provides evidence against the caloric theory of heat? a) Heat does not flow from hot objects to cold objects b) Adding more heat to ice water does not raise the temperature c) Steam engines do not run efficiently when they are cold. d) in a steam engine, heat flows from the hot parts to the cool parts of the engine 4. What breakthrough is said to mark the true beginning of the field of thermodynamics? a) The discovery of a substance called “caloric.” b) The invention of the thermometer. c) The discovery of latent heat. d) The invention of the electric motor. 5. Which statement is true about the First Law of Thermodynamics? a) It states that energy cannot be created. b) It states that energy cannot be destroyed. c) It is another name for the Law of Conservation of Energy. d) All choices are correct. -----------------End of Second Quarter ---------------