# High School Physics Friction

Section 2: Force: Lecture 6 | 50:11 min

So, we know about forces, multi-dimensional kinematics, and Newton’s 3 laws of motion; now it’s time to add some real-world aspects to our problems. Friction is a way of objects trying to stay put and not move. Friction can be thought of as an anti-force; it tries to keep objects from moving and stop objects in motion. Since friction is a force, unless otherwise stated, it should be included in your free-body diagrams from now on, and factor into any calculation of which it is relevant. Next time we’ll finish our force discussion in mechanics.

Vincent Selhorst-Jones

Friction

Slide Duration:Table of Contents

16m 49s

- Intro0:00
- The Metric System0:26
- Distance, Mass, Volume, and Time0:27
- Scientific Notation1:40
- Examples: 47,000,000,000 and 0.000000021:41
- Significant Figures3:18
- Significant Figures Overview3:19
- Properties of Significant Figures4:04
- How Significant Figures Interact7:00
- Trigonometry Review8:57
- Pythagorean Theorem, sine, cosine, and tangent8:58
- Inverse Trigonometric Functions9:48
- Inverse Trigonometric Functions9:49
- Vectors10:44
- Vectors10:45
- Scalars12:10
- Scalars12:11
- Breaking a Vector into Components13:17
- Breaking a Vector into Components13:18
- Length of a Vector13:58
- Length of a Vector13:59
- Relationship Between Length, Angle, and Coordinates14:45

26m 2s

- Intro0:00
- Position0:06
- Definition and Example of Position0:07
- Distance1:11
- Definition and Example of Distance1:12
- Displacement1:34
- Definition and Example of Displacement1:35
- Comparison2:45
- Distance vs. Displacement2:46
- Notation2:54
- Notation for Location, Distance, and Displacement2:55
- Speed3:32
- Definition and Formula for Speed3:33
- Example: Speed3:51
- Velocity4:23
- Definition and Formula for Velocity4:24
- ∆ - Greek: 'Delta'5:01
- ∆ or 'Change In'5:02
- Acceleration6:02
- Definition and Formula for Acceleration6:03
- Example: Acceleration6:38
- Gravity7:31
- Gravity7:32
- Formulas8:44
- Kinematics Formula 18:45
- Kinematics Formula 29:32
- Definitional Formulas14:00
- Example 1: Speed of a Rock Being Thrown14:12
- Example 2: How Long Does It Take for the Rock to Hit the Ground?15:37
- Example 3: Acceleration of a Biker21:09
- Example 4: Velocity and Displacement of a UFO22:43

29m 59s

- Intro0:00
- What's Different About Multiple Dimensions?0:07
- Scalars and Vectors0:08
- A Note on Vectors2:12
- Indicating Vectors2:13
- Position3:03
- Position3:04
- Distance and Displacement3:35
- Distance and Displacement: Definitions3:36
- Distance and Displacement: Example4:39
- Speed and Velocity8:57
- Speed and Velocity: Definition & Formulas8:58
- Speed and Velocity: Example10:06
- Speed from Velocity12:01
- Speed from Velocity12:02
- Acceleration14:09
- Acceleration14:10
- Gravity14:26
- Gravity14:27
- Formulas15:11
- Formulas with Vectors15:12
- Example 1: Average Acceleration16:57
- Example 2A: Initial Velocity19:14
- Example 2B: How Long Does It Take for the Ball to Hit the Ground?21:35
- Example 2C: Displacement26:46

18m 36s

- Intro0:00
- Fundamental Example0:25
- Fundamental Example Part 10:26
- Fundamental Example Part 21:20
- General Case2:36
- Particle P and Two Observers A and B2:37
- Speed of P from A's Frame of Reference3:05
- What About Acceleration?3:22
- Acceleration Shows the Change in Velocity3:23
- Acceleration when Velocity is Constant3:48
- Multi-Dimensional Case4:35
- Multi-Dimensional Case4:36
- Some Notes5:04
- Choosing the Frame of Reference5:05
- Example 1: What Velocity does the Ball have from the Frame of Reference of a Stationary Observer?7:27
- Example 2: Velocity, Speed, and Displacement9:26
- Example 3: Speed and Acceleration in the Reference Frame12:44

16m 34s

- Intro0:00
- Centripetal Acceleration1:21
- Centripetal Acceleration of a Rock Being Twirled Around on a String1:22
- Looking Closer: Instantaneous Velocity and Tangential Velocity2:35
- Magnitude of Acceleration3:55
- Centripetal Acceleration Formula5:14
- You Say You Want a Revolution6:11
- What is a Revolution?6:12
- How Long Does it Take to Complete One Revolution Around the Circle?6:51
- Example 1: Centripetal Acceleration of a Rock7:40
- Example 2: Magnitude of a Car's Acceleration While Turning9:20
- Example 3: Speed of a Point on the Edge of a US Quarter13:10

12m 37s

- Intro0:00
- Newton's First Law/ Law of Inertia2:45
- A Body's Velocity Remains Constant Unless Acted Upon by a Force2:46
- Mass & Inertia4:07
- Mass & Inertia4:08
- Mass & Volume5:49
- Mass & Volume5:50
- Mass & Weight7:08
- Mass & Weight7:09
- Example 1: The Speed of a Rocket8:47
- Example 2: Which of the Following Has More Inertia?10:06
- Example 3: Change in Inertia11:51

27m 5s

- Intro0:00
- Net Force1:42
- Consider a Block That is Pushed On Equally From Both Sides1:43
- What if One of the Forces was Greater Than the Other?2:29
- The Net Force is All the Forces Put Together2:43
- Newton's Second Law3:14
- Net Force = (Mass) x (Acceleration)3:15
- Units3:48
- The Units of Newton's Second Law3:49
- Free-Body Diagram5:34
- Free-Body Diagram5:35
- Special Forces: Gravity (Weight)8:05
- Force of Gravity8:06
- Special Forces: Normal Force9:22
- Normal Force9:23
- Special Forces: Tension10:34
- Tension10:35
- Example 1: Force and Acceleration12:19
- Example 2: A 5kg Block is Pushed by Five Forces13:24
- Example 3: A 10kg Block Resting On a Table is Tethered Over a Pulley to a Free-Hanging 2kg Block16:30

27m 47s

- Intro0:00
- Newton's 2nd Law in Multiple Dimensions0:12
- Newton's 2nd Law in Multiple Dimensions0:13
- Components0:52
- Components0:53
- Example: Force in Component Form1:02
- Special Forces2:39
- Review of Special Forces: Gravity, Normal Force, and Tension2:40
- Normal Forces3:35
- Why Do We Call It the Normal Forces?3:36
- Normal Forces on a Flat Horizontal and Vertical Surface5:00
- Normal Forces on an Incline6:05
- Example 1: A 5kg Block is Pushed By a Force of 3N to the North and a Force of 4N to the East10:22
- Example 2: A 20kg Block is On an Incline of 50° With a Rope Holding It In Place16:08
- Example 3: A 10kg Block is On an Incline of 20° Attached By Rope to a Free-hanging Block of 5kg20:50

42m 5s

- Intro0:00
- Block and Tackle Pulley System0:30
- A Single Pulley Lifting System0:31
- A Double Pulley Lifting System1:32
- A Quadruple Pulley Lifting System2:59
- Example 1: A Free-hanging, Massless String is Holding Up Three Objects of Unknown Mass4:40
- Example 2: An Object is Acted Upon by Three Forces10:23
- Example 3: A Chandelier is Suspended by a Cable From the Roof of an Elevator17:13
- Example 4: A 20kg Baboon Climbs a Massless Rope That is Attached to a 22kg Crate23:46
- Example 5: Two Blocks are Roped Together on Inclines of Different Angles33:17

16m 47s

- Intro0:00
- Newton's Third Law0:50
- Newton's Third Law0:51
- Everyday Examples1:24
- Hammer Hitting a Nail1:25
- Swimming2:08
- Car Driving2:35
- Walking3:15
- Note3:57
- Newton's Third Law Sometimes Doesn't Come Into Play When Solving Problems: Reason 13:58
- Newton's Third Law Sometimes Doesn't Come Into Play When Solving Problems: Reason 25:36
- Example 1: What Force Does the Moon Pull on Earth?7:04
- Example 2: An Astronaut in Deep Space Throwing a Wrench8:38
- Example 3: A Woman Sitting in a Bosun's Chair that is Hanging from a Rope that Runs Over a Frictionless Pulley12:51

50m 11s

- Intro0:00
- Introduction0:04
- Our Intuition - Materials0:30
- Our Intuition - Weight2:48
- Our Intuition - Normal Force3:45
- The Normal Force and Friction4:11
- Two Scenarios: Same Object, Same Surface, Different Orientations4:12
- Friction is Not About Weight6:36
- Friction as an Equation7:23
- Summing Up Friction7:24
- Friction as an Equation7:36
- The Direction of Friction10:33
- The Direction of Friction10:34
- A Quick Example11:16
- Which Block Will Accelerate Faster?11:17
- Static vs. Kinetic14:52
- Static vs. Kinetic14:53
- Static and Kinetic Coefficient of Friction16:31
- How to Use Static Friction17:40
- How to Use Static Friction17:41
- Some Examples of μs and μk19:51
- Some Examples of μs and μk19:52
- A Remark on Wheels22:19
- A Remark on Wheels22:20
- Example 1: Calculating μs and μk28:02
- Example 2: At What Angle Does the Block Begin to Slide?31:35
- Example 3: A Block is Against a Wall, Sliding Down36:30
- Example 4: Two Blocks Sitting Atop Each Other40:16

26m 45s

- Intro0:00
- Centripetal Force0:46
- Equations for Centripetal Force0:47
- Centripetal Force in Action1:26
- Where Does Centripetal Force Come From?2:39
- Where Does Centripetal Force Come From?2:40
- Centrifugal Force4:05
- Centrifugal Force Part 14:06
- Centrifugal Force Part 26:16
- Example 1: Part A - Centripetal Force On the Car8:12
- Example 1: Part B - Maximum Speed the Car Can Take the Turn At Without Slipping8:56
- Example 2: A Bucket Full of Water is Spun Around in a Vertical Circle15:13
- Example 3: A Rock is Spun Around in a Vertical Circle21:36

28m 34s

- Intro0:00
- Equivocation0:05
- Equivocation0:06
- Introduction to Work0:32
- Scenarios: 10kg Block on a Frictionless Table0:33
- Scenario: 2 Block of Different Masses2:52
- Work4:12
- Work and Force4:13
- Paralleled vs. Perpendicular4:46
- Work: A Formal Definition7:33
- An Alternate Formula9:00
- An Alternate Formula9:01
- Units10:40
- Unit for Work: Joule (J)10:41
- Example 1: Calculating Work of Force11:32
- Example 2: Work and the Force of Gravity12:48
- Example 3: A Moving Box & Force Pushing in the Opposite Direction15:11
- Example 4: Work and Forces with Directions18:06
- Example 5: Work and the Force of Gravity23:16

39m 7s

- Intro0:00
- Types of Energy0:04
- Types of Energy0:05
- Conservation of Energy1:12
- Conservation of Energy1:13
- What is Energy?4:23
- Energy4:24
- What is Work?5:01
- Work5:02
- Circular Definition, Much?5:46
- Circular Definition, Much?5:47
- Derivation of Kinetic Energy (Simplified)7:44
- Simplified Picture of Work7:45
- Consider the Following Three Formulas8:42
- Kinetic Energy Formula11:01
- Kinetic Energy Formula11:02
- Units11:54
- Units for Kinetic Energy11:55
- Conservation of Energy13:24
- Energy Cannot be Made or Destroyed, Only Transferred13:25
- Friction15:02
- How Does Friction Work?15:03
- Example 1: Velocity of a Block15:59
- Example 2: Energy Released During a Collision18:28
- Example 3: Speed of a Block22:22
- Example 4: Speed and Position of a Block26:22

28m 10s

- Intro0:00
- Why Is It Called Potential Energy?0:21
- Why Is It Called Potential Energy?0:22
- Introduction to Gravitational Potential Energy1:20
- Consider an Object Dropped from Ever-Increasing heights1:21
- Gravitational Potential Energy2:02
- Gravitational Potential Energy: Derivation2:03
- Gravitational Potential Energy: Formulas2:52
- Gravitational Potential Energy: Notes3:48
- Conservation of Energy5:50
- Conservation of Energy and Formula5:51
- Example 1: Speed of a Falling Rock6:31
- Example 2: Energy Lost to Air Drag10:58
- Example 3: Distance of a Sliding Block15:51
- Example 4: Swinging Acrobat21:32

44m 16s

- Intro0:00
- Introduction to Elastic Potential0:12
- Elastic Object0:13
- Spring Example1:11
- Hooke's Law3:27
- Hooke's Law3:28
- Example of Hooke's Law5:14
- Elastic Potential Energy Formula8:27
- Elastic Potential Energy Formula8:28
- Conservation of Energy10:17
- Conservation of Energy10:18
- You Ain't Seen Nothin' Yet12:12
- You Ain't Seen Nothin' Yet12:13
- Example 1: Spring-Launcher13:10
- Example 2: Compressed Spring18:34
- Example 3: A Block Dangling From a Massless Spring24:33
- Example 4: Finding the Spring Constant36:13

28m 54s

- Intro0:00
- Introduction to Power & Simple Machines0:06
- What's the Difference Between a Go-Kart, a Family Van, and a Racecar?0:07
- Consider the Idea of Climbing a Flight of Stairs1:13
- Power2:35
- P= W / t2:36
- Alternate Formulas2:59
- Alternate Formulas3:00
- Units4:24
- Units for Power: Watt, Horsepower, and Kilowatt-hour4:25
- Block and Tackle, Redux5:29
- Block and Tackle Systems5:30
- Machines in General9:44
- Levers9:45
- Ramps10:51
- Example 1: Power of Force12:22
- Example 2: Power &Lifting a Watermelon14:21
- Example 3: Work and Instantaneous Power16:05
- Example 4: Power and Acceleration of a Race car25:56

36m 55s

- Intro0:00
- Introduction to Center of Mass0:04
- Consider a Ball Tossed in the Air0:05
- Center of Mass1:27
- Definition of Center of Mass1:28
- Example of center of Mass2:13
- Center of Mass: Derivation4:21
- Center of Mass: Formula6:44
- Center of Mass: Formula, Multiple Dimensions8:15
- Center of Mass: Symmetry9:07
- Center of Mass: Non-Homogeneous11:00
- Center of Gravity12:09
- Center of Mass vs. Center of Gravity12:10
- Newton's Second Law and the Center of Mass14:35
- Newton's Second Law and the Center of Mass14:36
- Example 1: Finding The Center of Mass16:29
- Example 2: Finding The Center of Mass18:55
- Example 3: Finding The Center of Mass21:46
- Example 4: A Boy and His Mail28:31

22m 50s

- Intro0:00
- Introduction to Linear Momentum0:04
- Linear Momentum Overview0:05
- Consider the Scenarios0:45
- Linear Momentum1:45
- Definition of Linear Momentum1:46
- Impulse3:10
- Impulse3:11
- Relationship Between Impulse & Momentum4:27
- Relationship Between Impulse & Momentum4:28
- Why is It Linear Momentum?6:55
- Why is It Linear Momentum?6:56
- Example 1: Momentum of a Skateboard8:25
- Example 2: Impulse and Final Velocity8:57
- Example 3: Change in Linear Momentum and magnitude of the Impulse13:53
- Example 4: A Ball of Putty17:07

40m 55s

- Intro0:00
- Investigating Collisions0:45
- Momentum0:46
- Center of Mass1:26
- Derivation1:56
- Extending Idea of Momentum to a System1:57
- Impulse5:10
- Conservation of Linear Momentum6:14
- Conservation of Linear Momentum6:15
- Conservation and External Forces7:56
- Conservation and External Forces7:57
- Momentum Vs. Energy9:52
- Momentum Vs. Energy9:53
- Types of Collisions12:33
- Elastic12:34
- Inelastic12:54
- Completely Inelastic13:24
- Everyday Collisions and Atomic Collisions13:42
- Example 1: Impact of Two Cars14:07
- Example 2: Billiard Balls16:59
- Example 3: Elastic Collision23:52
- Example 4: Bullet's Velocity33:35

34m 53s

- Intro0:00
- Law of Universal Gravitation1:39
- Law of Universal Gravitation1:40
- Force of Gravity Equation2:14
- Gravitational Field5:38
- Gravitational Field Overview5:39
- Gravitational Field Equation6:32
- Orbits9:25
- Orbits9:26
- The 'Falling' Moon12:58
- The 'Falling' Moon12:59
- Example 1: Force of Gravity17:05
- Example 2: Gravitational Field on the Surface of Earth20:35
- Example 3: Orbits23:15
- Example 4: Neutron Star28:38

35m 35s

- Intro0:00
- Pulse1:00
- Introduction to Pulse1:01
- Wave1:59
- Wave Overview2:00
- Wave Types3:16
- Mechanical Waves3:17
- Electromagnetic Waves4:01
- Matter or Quantum Mechanical Waves4:43
- Transverse Waves5:12
- Longitudinal Waves6:24
- Wave Characteristics7:24
- Amplitude and Wavelength7:25
- Wave Speed (v)10:13
- Period (T)11:02
- Frequency (f)12:33
- v = λf14:51
- Wave Equation16:15
- Wave Equation16:16
- Angular Wave Number17:34
- Angular Frequency19:36
- Example 1: CPU Frequency24:35
- Example 2: Speed of Light, Wavelength, and Frequency26:11
- Example 3: Spacing of Grooves28:35
- Example 4: Wave Diagram31:21

52m 57s

- Intro0:00
- Superposition0:38
- Superposition0:39
- Interference1:31
- Interference1:32
- Visual Example: Two Positive Pulses2:33
- Visual Example: Wave4:02
- Phase of Cycle6:25
- Phase Shift7:31
- Phase Shift7:32
- Standing Waves9:59
- Introduction to Standing Waves10:00
- Visual Examples: Standing Waves, Node, and Antinode11:27
- Standing Waves and Wavelengths15:37
- Standing Waves and Resonant Frequency19:18
- Doppler Effect20:36
- When Emitter and Receiver are Still20:37
- When Emitter is Moving Towards You22:31
- When Emitter is Moving Away24:12
- Doppler Effect: Formula25:58
- Example 1: Superposed Waves30:00
- Example 2: Superposed and Fully Destructive Interference35:57
- Example 3: Standing Waves on a String40:45
- Example 4: Police Siren43:26
- Example Sounds: 800 Hz, 906.7 Hz, 715.8 Hz, and Slide 906.7 to 715.8 Hz48:49

36m 24s

- Intro0:00
- Speed of Sound1:26
- Speed of Sound1:27
- Pitch2:44
- High Pitch & Low Pitch2:45
- Normal Hearing3:45
- Infrasonic and Ultrasonic4:02
- Intensity4:54
- Intensity: I = P/A4:55
- Intensity of Sound as an Outwardly Radiating Sphere6:32
- Decibels9:09
- Human Threshold for Hearing9:10
- Decibel (dB)10:28
- Sound Level β11:53
- Loudness Examples13:44
- Loudness Examples13:45
- Beats15:41
- Beats & Frequency15:42
- Audio Examples of Beats17:04
- Sonic Boom20:21
- Sonic Boom20:22
- Example 1: Firework23:14
- Example 2: Intensity and Decibels24:48
- Example 3: Decibels28:24
- Example 4: Frequency of a Violin34:48

19m 38s

- Intro0:00
- The Speed of Light0:31
- Speed of Light in a Vacuum0:32
- Unique Properties of Light1:20
- Lightspeed!3:24
- Lightyear3:25
- Medium4:34
- Light & Medium4:35
- Electromagnetic Spectrum5:49
- Electromagnetic Spectrum Overview5:50
- Electromagnetic Wave Classifications7:05
- Long Radio Waves & Radio Waves7:06
- Microwave8:30
- Infrared and Visible Spectrum9:02
- Ultraviolet, X-rays, and Gamma Rays9:33
- So Much Left to Explore11:07
- So Much Left to Explore11:08
- Example 1: How Much Distance is in a Light-year?13:16
- Example 2: Electromagnetic Wave16:50
- Example 3: Radio Station & Wavelength17:55

42m 52s

- Intro0:00
- Fluid?0:48
- What Does It Mean to be a Fluid?0:49
- Density1:46
- What is Density?1:47
- Formula for Density: ρ = m/V2:25
- Pressure3:40
- Consider Two Equal Height Cylinders of Water with Different Areas3:41
- Definition and Formula for Pressure: p = F/A5:20
- Pressure at Depth7:02
- Pressure at Depth Overview7:03
- Free Body Diagram for Pressure in a Container of Fluid8:31
- Equations for Pressure at Depth10:29
- Absolute Pressure vs. Gauge Pressure12:31
- Absolute Pressure vs. Gauge Pressure12:32
- Why Does Gauge Pressure Matter?13:51
- Depth, Not Shape or Direction15:22
- Depth, Not Shape or Direction15:23
- Depth = Height18:27
- Depth = Height18:28
- Buoyancy19:44
- Buoyancy and the Buoyant Force19:45
- Archimedes' Principle21:09
- Archimedes' Principle21:10
- Wait! What About Pressure?22:30
- Wait! What About Pressure?22:31
- Example 1: Rock & Fluid23:47
- Example 2: Pressure of Water at the Top of the Reservoir28:01
- Example 3: Wood & Fluid31:47
- Example 4: Force of Air Inside a Cylinder36:20

34m 6s

- Intro0:00
- Absolute Zero1:50
- Absolute Zero1:51
- Kelvin2:25
- Kelvin2:26
- Heat vs. Temperature4:21
- Heat vs. Temperature4:22
- Heating Water5:32
- Heating Water5:33
- Specific Heat7:44
- Specific Heat: Q = cm(∆T)7:45
- Heat Transfer9:20
- Conduction9:24
- Convection10:26
- Radiation11:35
- Example 1: Converting Temperature13:21
- Example 2: Calories14:54
- Example 3: Thermal Energy19:00
- Example 4: Temperature When Mixture Comes to Equilibrium Part 120:45
- Example 4: Temperature When Mixture Comes to Equilibrium Part 224:55

44m 3s

- Intro0:00
- Linear Expansion1:06
- Linear Expansion: ∆L = Lα(∆T)1:07
- Volume Expansion2:34
- Volume Expansion: ∆V = Vβ(∆T)2:35
- Gas Expansion3:40
- Gas Expansion3:41
- The Mole5:43
- Conceptual Example5:44
- The Mole and Avogadro's Number7:30
- Ideal Gas Law9:22
- Ideal Gas Law: pV = nRT9:23
- p = Pressure of the Gas10:07
- V = Volume of the Gas10:34
- n = Number of Moles of Gas10:44
- R = Gas Constant10:58
- T = Temperature11:58
- A Note On Water12:21
- A Note On Water12:22
- Change of Phase15:55
- Change of Phase15:56
- Change of Phase and Pressure17:31
- Phase Diagram18:41
- Heat of Transformation20:38
- Heat of Transformation: Q = Lm20:39
- Example 1: Linear Expansion22:38
- Example 2: Explore Why β = 3α24:40
- Example 3: Ideal Gas Law31:38
- Example 4: Heat of Transformation38:03

27m 30s

- Intro0:00
- First Law of Thermodynamics1:11
- First Law of Thermodynamics1:12
- Engines2:25
- Conceptual Example: Consider a Piston2:26
- Second Law of Thermodynamics4:17
- Second Law of Thermodynamics4:18
- Entropy6:09
- Definition of Entropy6:10
- Conceptual Example of Entropy: Stick of Dynamite7:00
- Order to Disorder8:22
- Order and Disorder in a System8:23
- The Poets Got It Right10:20
- The Poets Got It Right10:21
- Engines in General11:21
- Engines in General11:22
- Efficiency12:06
- Measuring the Efficiency of a System12:07
- Carnot Engine ( A Limit to Efficiency)13:20
- Carnot Engine & Maximum Possible Efficiency13:21
- Example 1: Internal Energy15:15
- Example 2: Efficiency16:13
- Example 3: Second Law of Thermodynamics17:05
- Example 4: Maximum Efficiency20:10

41m 35s

- Intro0:00
- Charge1:04
- Overview of Charge1:05
- Positive and Negative Charges1:19
- A Simple Model of the Atom2:47
- Protons, Electrons, and Neutrons2:48
- Conservation of Charge4:47
- Conservation of Charge4:48
- Elementary Charge5:41
- Elementary Charge and the Unit Coulomb5:42
- Coulomb's Law8:29
- Coulomb's Law & the Electrostatic Force8:30
- Coulomb's Law Breakdown9:30
- Conductors and Insulators11:11
- Conductors11:12
- Insulators12:31
- Conduction15:08
- Conduction15:09
- Conceptual Examples15:58
- Induction17:02
- Induction Overview17:01
- Conceptual Examples18:18
- Example 1: Electroscope20:08
- Example 2: Positive, Negative, and Net Charge of Iron22:15
- Example 3: Charge and Mass27:52
- Example 4: Two Metal Spheres31:58

34m 44s

- Intro0:00
- Electric Fields0:53
- Electric Fields Overview0:54
- Size of q2 (Second Charge)1:34
- Size of q1 (First Charge)1:53
- Electric Field Strength: Newtons Per Coulomb2:55
- Electric Field Lines4:19
- Electric Field Lines4:20
- Conceptual Example 15:17
- Conceptual Example 26:20
- Conceptual Example 36:59
- Conceptual Example 47:28
- Faraday Cage8:47
- Introduction to Faraday Cage8:48
- Why Does It Work?9:33
- Electric Potential Energy11:40
- Electric Potential Energy11:41
- Electric Potential13:44
- Electric Potential13:45
- Difference Between Two States14:29
- Electric Potential is Measured in Volts15:12
- Ground Voltage16:09
- Potential Differences and Reference Voltage16:10
- Ground Voltage17:20
- Electron-volt19:17
- Electron-volt19:18
- Equipotential Surfaces20:29
- Equipotential Surfaces20:30
- Equipotential Lines21:21
- Equipotential Lines21:22
- Example 1: Electric Field22:40
- Example 2: Change in Energy24:25
- Example 3: Constant Electrical Field27:06
- Example 4: Electrical Field and Change in Voltage29:06
- Example 5: Voltage and Energy32:14

29m 12s

- Intro0:00
- Electric Current0:31
- Electric Current0:32
- Amperes1:27
- Moving Charge1:52
- Conceptual Example: Electric Field and a Conductor1:53
- Voltage3:26
- Resistance5:05
- Given Some Voltage, How Much Current Will Flow?5:06
- Resistance: Definition and Formula5:40
- Resistivity7:31
- Resistivity7:32
- Resistance for a Uniform Object9:31
- Energy and Power9:55
- How Much Energy Does It take to Move These Charges Around?9:56
- What Do We Call Energy Per Unit Time?11:08
- Formulas to Express Electrical Power11:53
- Voltage Source13:38
- Introduction to Voltage Source13:39
- Obtaining a Voltage Source: Generator15:15
- Obtaining a Voltage Source: Battery16:19
- Speed of Electricity17:17
- Speed of Electricity17:18
- Example 1: Electric Current & Moving Charge19:40
- Example 2: Electric Current & Resistance20:31
- Example 3: Resistivity & Resistance21:56
- Example 4: Light Bulb25:16

52m 2s

- Intro0:00
- Electric Circuits0:51
- Current, Voltage, and Circuit0:52
- Resistor5:05
- Definition of Resistor5:06
- Conceptual Example: Lamps6:18
- Other Fundamental Components7:04
- Circuit Diagrams7:23
- Introduction to Circuit Diagrams7:24
- Wire7:42
- Resistor8:20
- Battery8:45
- Power Supply9:41
- Switch10:02
- Wires: Bypass and Connect10:53
- A Special Not in General12:04
- Example: Simple vs. Complex Circuit Diagram12:45
- Kirchoff's Circuit Laws15:32
- Kirchoff's Circuit Law 1: Current Law15:33
- Kirchoff's Circuit Law 1: Visual Example16:57
- Kirchoff's Circuit Law 2: Voltage Law17:16
- Kirchoff's Circuit Law 2: Visual Example19:23
- Resistors in Series21:48
- Resistors in Series21:49
- Resistors in Parallel23:33
- Resistors in Parallel23:34
- Voltmeter and Ammeter28:35
- Voltmeter28:36
- Ammeter30:05
- Direct Current vs. Alternating Current31:24
- Direct Current vs. Alternating Current31:25
- Visual Example: Voltage Graphs33:29
- Example 1: What Voltage is Read by the Voltmeter in This Diagram?33:57
- Example 2: What Current Flows Through the Ammeter When the Switch is Open?37:42
- Example 3: How Much Power is Dissipated by the Highlighted Resistor When the Switch is Open? When Closed?41:22
- Example 4: Design a Hallway Light Switch45:14

25m 47s

- Intro0:00
- Magnet1:27
- Magnet Has Two Poles1:28
- Magnetic Field1:47
- Always a Dipole, Never a Monopole2:22
- Always a Dipole, Never a Monopole2:23
- Magnetic Fields and Moving Charge4:01
- Magnetic Fields and Moving Charge4:02
- Magnets on an Atomic Level4:45
- Magnets on an Atomic Level4:46
- Evenly Distributed Motions5:45
- Unevenly Distributed Motions6:22
- Current and Magnetic Fields9:42
- Current Flow and Magnetic Field9:43
- Electromagnet11:35
- Electric Motor13:11
- Electric Motor13:12
- Generator15:38
- A Changing Magnetic Field Induces a Current15:39
- Example 1: What Kind of Magnetic Pole must the Earth's Geographic North Pole Be?19:34
- Example 2: Magnetic Field and Generator/Electric Motor20:56
- Example 3: Destroying the Magnetic Properties of a Permanent Magnet23:08

For more information, please see full course syllabus of High School Physics

1 answer

Last reply by: Professor Selhorst-Jones

Wed Apr 1, 2020 10:14 AM

Post by beihur777 on April 1 at 12:11:32 AM

Is the normal force always equal to the force of gravity. Let's say that there is a block that is being acted on by a force upward. Would the normal force be equal to the force of gravity minus the upward force, or would it just be equal to the force of gravity?

1 answer

Last reply by: Professor Selhorst-Jones

Mon May 15, 2017 11:32 PM

Post by sania sarwar on April 26, 2017

which geometry lesson would you recommend in order to understand example 2's math?

1 answer

Last reply by: Professor Selhorst-Jones

Fri Mar 25, 2016 6:25 PM

Post by Peter Ke on March 7, 2016

At 49:29, why F_fric=m_2*a and not F_fric=u_s*m_2*g?

1 answer

Last reply by: Professor Selhorst-Jones

Mon Oct 6, 2014 11:59 AM

Post by Tori Carroll on October 5, 2014

I have a question on a problem similar to your third example. Say a box of mass m is held at rest against a vertical wall by a horizontal force FA. The wall has coefficient of friction Î¼. How would you solve for the minimum coefficient of friction Î¼ in terms of FA, m, and g?

1 answer

Last reply by: Professor Selhorst-Jones

Sun Jul 28, 2013 9:01 PM

Post by enya zh on July 27, 2013

Which type of objects have greater static friction than kinetic friction? Just curious.:)

Thanks!!!:):)

1 answer

Last reply by: Professor Selhorst-Jones

Sun Oct 28, 2012 9:49 PM

Post by varsha sharma on October 28, 2012

in example 3 shouldn't it be

mg-fric.= 0 ( because the object is moving down )

(though by doing your way ,the answer will be the same)

3 answers

Last reply by: Professor Selhorst-Jones

Wed Oct 17, 2012 1:58 PM

Post by Nik Googooli on August 30, 2012

50/m.g=

50/98=0.51 not 0.71

1 answer

Last reply by: Professor Selhorst-Jones

Thu Sep 6, 2012 4:48 PM

Post by Patrick Gomez on August 7, 2012

I love Physics! It's amazing how a person's whole way of viewing the world around them changes as they continue to learn more.