1	TAKS Objective 5 Motion , Forces and Energy
2	Energy Is defined as the Ability to do Work Energy has Two Types:
3	Kinetic Energy KE = ½ m v ² Ex: A moving car has the ability to do work on the light pole if it hits it.
4	Potential Energy 2 possibilities Gravitational PE -Object lifted to some height Elastic PE - A stretched or compressed object (spring or rubber band)
5	Gravitational Potential Energy or Will it fall? GPE = m g h m is the mass of the object in Kg, g is the acceleration due to gravity which is 9.8 m/s² on earth and h is the height in meters
6	Use the formula page! PE = mgh
7	Law of Conservation of Energy Energy can change forms, but is never created nor destroyed Loss in one form = gain in an another form A falling object speeds up as it falls to the ground; PE decreases as KE increases. The KE it has at impact = the PE it had before it fell.
8	Example: A falling object speeds up as it falls to the ground; PE decreases as KE increases, the KE it has at impact with the ground is equal to the PE it had before it fell
9	Energy can be conserved in Non-Mechanical forms The chemical energy in a battery transforms into electrical energy Any reaction where more energy is given off than is used to start it is Exogonic An Endogonic reaction absorbs energy and causes cooling
10	Electrical Energy - Moving electrons in a path is electricity Electrical Potential Difference (v) is measured in Volts The rate of moving electric charges, Electric Current (I), is measured in Amperes Resistance or opposition to the movement of the energy is called Resistance (R).
11	Circuits – 2 types Series circuits are the most simple. One (1) path for the current to travel. Contains an energy source, a path, and a load (something for it to do, like a lamp)
12	Circuits – 2 types Parallel circuits provide more than one path for the current to travel. Most circuits are parallel, since if one lamp goes out, the others can stay lit.
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14	USE THE FORMULA SHEET!! What is the current in a copper wire that has a resistance of 2 ohms and is connected to a 9 volt electrical source? A. 0.22 amp B. 4.5 amps C. 11.0 amps D. 18.0 amps
15	Thermal Energy A body contains internal KE due to the motion of its atoms ( they are constantly wiggling and jiggling) Thermal Energy is the total internal KE of a body Temperature is the average KE of a body
16	Heat- Transfer of Thermal Energy 1. Conduction-direct contact, a pot heating on a stove (solids) 2. Convection- heating by circulating fluids, (gas and liquid) heating from a fireplace And. . .
17	3. Radiation – Transfer of Electromagnetic (E.M.) Energy Objects are heated when exposed to infrared radiation The suns heats the earth by sending infrared radiation along with other forms of E.M. energy 3.0 x 10⁸ meters through empty space
18	Heat moves by conduction in solids since the particles are close together and vibrate. . . 43 Heat convection occurs in gases and liquids. Heat convection does not occur in solids because solids are unable to — A absorb heat by vibrating B transfer heat by fluid motion C emit radiation by reflecting light D exchange heat by direct contact
19	2 The primary way liquids and gases transmit heat is by the process of — F reflection G conduction H radiation J convection
20	"F improve emission of infrared..." F improve emission of infrared radiation G reduce the heat loss by convection currents H improve absorption of infrared radiation J reduce the heater’s conducting properties
21	Nuclear Reactions Fusion occurs when two atoms combine to form a new element. The sun produces all of its energy through fusion. Two hydrogen atoms combine to form a Helium atom from the great gravitational forces and pressure in the sun’s core
22	Nuclear Reactions - Fission Fission is the splitting of nucleii of large atoms such as Uranium and Plutonium Produces large amounts of infrared radiation and other forms of E.M. Energy such as Gamma Rays Currently, it is the main form of Atomic Energy on Earth
23	Radiant Energy or Electromagnetic Energy (EM) All radiant energy travels at 3.0 x 10⁸ m/sec in space Velocity of a wave = wavelength x frequency Visible light is just one type of EM Energy
24	Electromagnetic Spectrum Radiation comes in the form of vibrating or “throbbing bundles of energy” called photons The frequency of the vibrating electric charges determines which type and how much energy will be given off
25	The entire E.M. Spectrum in order from lowest to highest frequency Radio waves: AM and FM Microwaves: cooking Infrared: heat Visible: (ROYGBV) Ultraviolet: tanning Xrays: medical Gamma:
26	Waves - Energy carried by rhythmic disturbances Two types: 1. E.M. radiation move through empty space 2. Mechanical require a medium (air, water or any type of matter) for movement
27	Waves - 2 Types
28	All waves have similar properties Frequency- the number of vibrations per second or the speed of the movement of the vibrating particles Amplitude – the size of the movement of the vibrating particles Both are controlled by the disturbance that created the waves
29	Velocity of all waves - v=f λ f-frequency and λ is wavelength (distance between identical points on two consecutive waves) Reflection- bounce off barriers in regular ways Refraction- waves can change direction when speed changes
30	And the answer is? 38 At 0°C sound travels through air at a speed of 330 m/s. If a sound wave is produced with a wavelength of 0.10 m, what is the wave’s frequency? F 0.0033 Hz G 33 Hz H 330 Hz J 3300 Hz
31	Transverse Waves In Transverse Waves particles vibrate at right angles to the direction the wave travels. Ex. E. M. Waves, waves on a slinky or rope coil, ocean waves
32	Longitudinal or Compress ional Waves Vibrating particles move back and forth along the direction of the wave velocity Parts consist of compressions and rarefactions Ex. Sound Waves
33	Sound Waves are Compression Waves Sound is produced when a compression is made. It requires a producer and a medium to travel through. The more elastic the object, the faster sound travels.
34	Sound acts like other waves Echoes are reflected sound waves Sonar uses echoes to judge distance to obstructions Human hearing is 20-20,000 Hz, below 10 Hz is infrasonic, and above 20,000 Hz is ultrasonic.
35	Sound Waves move through matter not through empty space. 32 One tuning fork is struck and placed next to an identical fork. The two forks do not touch. The second tuning fork starts to vibrate because of — F interference G the Doppler effect H resonance J standing waves
36	Forces and Motion Forces can create changes in motion (acceleration) Deceleration is negative acceleration
37	Motion can be described as a change in an object’s position Average velocity (speed) is the change of position of an object over time
38	Velocity Graphs V = distance time Velocity (v) is the slope (rise over run) of a position (d) vs. time (t) graph
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40	Acceleration Graphs Acceleration (a) is the slope of a velocity (v) vs. time (t) graph Plotted on a distance vs. time graph, acceleration is an exponential curve
41	Acceleration is a change in an objects velocity (speed or direction) When an object’s speed changes over time it is accelerating (or decelerating) A = v_final – v_initial time Units for acceleration m/s/s or m/s²
42	Definition of a Force A Force is a push or a pull
43	Balanced Force A force that produces no change in an object’s motion because it is balanced by an equal, opposite force.
44	4 The picture shows the position of a ball every 0.25 second on a photogram. Using a ruler, determine the velocity of the ball. F 3.5 cm/s G 10.5 cm/s H 14.0 cm/s J 28.0 cm/s
45	Use the ruler on the side of the chart and the equation for velocity. The answer was H.
46	Unbalanced Forces Are forces that results in an object’s motion being changed.
47	Friction A force that acts in a direction opposite to the motion of two surfaces in contact with each other.
48	Friction Friction causes an object to slow down and stop. Since the amount of energy stays constant, the energy becomes heat.
49	Newton’s 1st Law of Motion Object in motion stays in motion
50	Newton’s 1st Law of Motion And Objects at rest stay at rest
51	Newton’s 1st Law of Motion Until they are acted upon by unbalanced forces.
52	Inertia or Newtons 1^st Law Tendency for an object to stay at rest or moving in a straight line at a constant speed. The mass (m measured in kg) of an object determines its inertia
53	Newton’s 2nd Law of Motion Force = Mass X Acceleration F=ma Weight (pull of gravity) is a commonly measured force, calculated by F=mg, g is the acceleration due to gravity 9.8 m/s²
54	Newton’s 2nd Law of Motion The greater the mass of an object, the greater the force required to change its motion.
55	Newton’s 2nd Law of Motion The greater the acceleration of an object, the greater the force required to change its motion.
56	"A 0.2 N" A 0.2 N B 0.8 N C 1.5 N D 6.0 N
57	Newton’s 3rd Law of Motion For every action force there is an equal and opposite reaction force.
58	Newton’s 3^rd Law of Motion All forces come in action-reaction pairs Ex: feet push backward on floor, the floor pushes forward on feet
59	27 A ball moving at 30 m/s has a momentum of 15 kg·m/s. The mass of the ball is — A 45 kg B 15 kg C 2.0 kg D 0.5 kg
60	Work Work: using a force for a distance W = F x d The work done by forces on an object = changes in energy for that object. Work and Energy are measured in Joules 1 Joule=1 Newton • meter
61	"42 How much work is..." 42 How much work is performed when a 50 kg crate is pushed 15 m with a force of 20 N? F 300 J G 750 J H 1,000 J J 15,000 J
62	Why use a machine? In an ideal (perfect) machine the work put into the machine (W_in) = the work put out by that machine (W_out)
63	Machines make work easier The ideal mechanical advantage of a machine (IMA) of a machine is the number of times the output force is larger than the input force IMA=F_out/F_in A machine can only make this happen by moving the input force through a farther distance than the output force F_in • d_in=F_out • d_out
64	"48 The diagram shows an..."
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66	Real Machines use Energy No real machine is 100 % efficient. i.e. none put out more work than is put in Efficiency of a machine is work output/work input X 100 % Eff = W_outX 100% ^W_in
67	Machines use power Power: the rate at which energy is used (work is done) P=Work/time Power is measured in H.P. or watts 1 watt = 1 Joule ^{1 sec}
68	"A accelerated rapidly" A accelerated rapidly B remained motionless C decreased its velocity D gained momentum
69	6 Types of simple machines Some Simple Machines: Inclined planes Screws Pulleys Wheel and axle Levers Wedge
70	Universal Law of Gravitation All objects in the universe attract each other by the force of gravity
71	Universal Law of Gravitation Gravity varies depending on two factors:
72	On Earth gravity = 9.8 m/s/s For every second that an object falls its speed increases by 9.8 m/s
73	Weight= Mass (m) X gravity (g) Weight Unit of mass = kg Unit of acceleration = m/s/s Unit of weight = Newton 1 Newton= about ¼ pound
74	USE THE FORMULA PAGE Some of the problems require you to grid in an answer. Make sure you pay attention to the decimal point in the square in the middle.