Welcome back, everyone. So in this problem, we have a wave function that's given to us. We have y(x,t) equals 6 millimeters, and then we have some numbers here. Right? We have 5 and then the units for this radians per millimeters, and then 600 radians per second. Some of the general sort of form of a wave function is that the first number is the amplitude, and the units. This is going to be the k value. Right? The thing goes in front of our x, and this is going to be the ω value. Alright? So what we want to do is we want to figure out how long it takes for something to happen. How long it takes for a given particle on the string to travel between plus 6 and negative 6 millimeters. So I sort of want to visualize what's going on here. If you take a string and sort of whip it up and down like this, you're going to get some sort of a sine wave, and the particles in the string remember are moving up and down. Now in this case, the amplitude of this wave is 6 millimeters. So basically, what is what's going to happen is that the particles on this, on the string are going to sort of bubble up and down between positive 6 and negative 6 millimeters over time. We're asked to find how long it takes for it to do that. Right? So a given particle on the string, it's going to sort of bounce up and down between these two points, the crest and the trough, forever. That's always what's going to happen, and we're trying to figure out how long it takes for that to happen. So Δt. Alright? So how do we solve for this? Well, the basic relationship between Δt and velocity and displacement is that v=ΔxΔt. Right? So displacement over time. So if I solve for this equation here, I can rearrange this in Δt=Δxv. Alright? So just very simply here, if I want to figure out time, I need to figure out the displacements, what's the distance that these particles are traveling, divided by what's the wave speed or what's the transverse velocity of the particles that are bobbing up and down. Alright? So how do I figure this out? What's the displacement? Well, the displacement really is just going to be the distance between the top of the crest and the bottom of the trough, and it's really just the distance between plus 6 and minus 6. In other words, it's basically just double the amplitude. So this is really just going to be 2 times amplitude, which is just going to be 12 millimeters. Alright. Now I can also convert this to 0.012, but that's basically where the displacement is. Alright? So that's done. So all I really need now is I need to figure out now the velocity, the display the velocity of the particles that are moving up and down on the string. And we have a new equation for this, it's the transverse velocity or whatever, and basically, the equation for the velocity is it's going to be the, I'm sorry. It's going to be the, the displacement velocity of the particles, which is going to be ω/k. Alright? So if we do do ω/k, basically, I'm just going to take this, ω, which is 600, and the units for this are going to be really important. So notice how I have 600. This is going to be radians per second divided by, and this is going to be 5, and this is going to be radians per millimeter here. Alright. So this is important because what happens is the radians are going to cancel when you do this, and what you end up getting is you end up getting a 120 millimeters per second. So the units are going to be really important here. So this is what my velocity is. It's a 120 millimeters per second. Alright. So then how do I figure it now Δt? Well, really now I have everything I need to solve, because now I have Δx and I have v. So I'm just going to bring this down here, and my Δt is just going to be my Δx, the displacement, which is 12 millimeters, divided by and this is going to be a 120 millimeters per second. So again, the units are important here because if you got something like meters and millimeters, you're going to have to convert. But what we're going to see here is that millimeters will cancel, and you're just going to be left with seconds. And really what happens is this is actually just going to be 0.1 seconds. So in other words, it takes 1 tenth of a second or 0.1 seconds for a particle in the string to sort of bounce up and down between positive 6 and negative 6. That's, will always happen. Alright? So it's kind of a strange problem. We're really sort of pulling together a lot of different equations from from wave functions. Let me know if you have any questions. Thanks for watching.
Table of contents
- 0. Math Review31m
- 1. Intro to Physics Units1h 24m
- 2. 1D Motion / Kinematics3h 56m
- Vectors, Scalars, & Displacement13m
- Average Velocity32m
- Intro to Acceleration7m
- Position-Time Graphs & Velocity26m
- Conceptual Problems with Position-Time Graphs22m
- Velocity-Time Graphs & Acceleration5m
- Calculating Displacement from Velocity-Time Graphs15m
- Conceptual Problems with Velocity-Time Graphs10m
- Calculating Change in Velocity from Acceleration-Time Graphs10m
- Graphing Position, Velocity, and Acceleration Graphs11m
- Kinematics Equations37m
- Vertical Motion and Free Fall19m
- Catch/Overtake Problems23m
- 3. Vectors2h 43m
- Review of Vectors vs. Scalars1m
- Introduction to Vectors7m
- Adding Vectors Graphically22m
- Vector Composition & Decomposition11m
- Adding Vectors by Components13m
- Trig Review24m
- Unit Vectors15m
- Introduction to Dot Product (Scalar Product)12m
- Calculating Dot Product Using Components12m
- Intro to Cross Product (Vector Product)23m
- Calculating Cross Product Using Components17m
- 4. 2D Kinematics1h 42m
- 5. Projectile Motion3h 6m
- 6. Intro to Forces (Dynamics)3h 22m
- 7. Friction, Inclines, Systems2h 44m
- 8. Centripetal Forces & Gravitation7h 26m
- Uniform Circular Motion7m
- Period and Frequency in Uniform Circular Motion20m
- Centripetal Forces15m
- Vertical Centripetal Forces10m
- Flat Curves9m
- Banked Curves10m
- Newton's Law of Gravity30m
- Gravitational Forces in 2D25m
- Acceleration Due to Gravity13m
- Satellite Motion: Intro5m
- Satellite Motion: Speed & Period35m
- Geosynchronous Orbits15m
- Overview of Kepler's Laws5m
- Kepler's First Law11m
- Kepler's Third Law16m
- Kepler's Third Law for Elliptical Orbits15m
- Gravitational Potential Energy21m
- Gravitational Potential Energy for Systems of Masses17m
- Escape Velocity21m
- Energy of Circular Orbits23m
- Energy of Elliptical Orbits36m
- Black Holes16m
- Gravitational Force Inside the Earth13m
- Mass Distribution with Calculus45m
- 9. Work & Energy1h 59m
- 10. Conservation of Energy2h 54m
- Intro to Energy Types3m
- Gravitational Potential Energy10m
- Intro to Conservation of Energy32m
- Energy with Non-Conservative Forces20m
- Springs & Elastic Potential Energy19m
- Solving Projectile Motion Using Energy13m
- Motion Along Curved Paths4m
- Rollercoaster Problems13m
- Pendulum Problems13m
- Energy in Connected Objects (Systems)24m
- Force & Potential Energy18m
- 11. Momentum & Impulse3h 40m
- Intro to Momentum11m
- Intro to Impulse14m
- Impulse with Variable Forces12m
- Intro to Conservation of Momentum17m
- Push-Away Problems19m
- Types of Collisions4m
- Completely Inelastic Collisions28m
- Adding Mass to a Moving System8m
- Collisions & Motion (Momentum & Energy)26m
- Ballistic Pendulum14m
- Collisions with Springs13m
- Elastic Collisions24m
- How to Identify the Type of Collision9m
- Intro to Center of Mass15m
- 12. Rotational Kinematics2h 59m
- 13. Rotational Inertia & Energy7h 4m
- More Conservation of Energy Problems54m
- Conservation of Energy in Rolling Motion45m
- Parallel Axis Theorem13m
- Intro to Moment of Inertia28m
- Moment of Inertia via Integration18m
- Moment of Inertia of Systems23m
- Moment of Inertia & Mass Distribution10m
- Intro to Rotational Kinetic Energy16m
- Energy of Rolling Motion18m
- Types of Motion & Energy24m
- Conservation of Energy with Rotation35m
- Torque with Kinematic Equations56m
- Rotational Dynamics with Two Motions50m
- Rotational Dynamics of Rolling Motion27m
- 14. Torque & Rotational Dynamics2h 5m
- 15. Rotational Equilibrium3h 39m
- 16. Angular Momentum3h 6m
- Opening/Closing Arms on Rotating Stool18m
- Conservation of Angular Momentum46m
- Angular Momentum & Newton's Second Law10m
- Intro to Angular Collisions15m
- Jumping Into/Out of Moving Disc23m
- Spinning on String of Variable Length20m
- Angular Collisions with Linear Motion8m
- Intro to Angular Momentum15m
- Angular Momentum of a Point Mass21m
- Angular Momentum of Objects in Linear Motion7m
- 17. Periodic Motion2h 9m
- 18. Waves & Sound3h 40m
- Intro to Waves11m
- Velocity of Transverse Waves21m
- Velocity of Longitudinal Waves11m
- Wave Functions31m
- Phase Constant14m
- Average Power of Waves on Strings10m
- Wave Intensity19m
- Sound Intensity13m
- Wave Interference8m
- Superposition of Wave Functions3m
- Standing Waves30m
- Standing Wave Functions14m
- Standing Sound Waves12m
- Beats8m
- The Doppler Effect7m
- 19. Fluid Mechanics4h 27m
- 20. Heat and Temperature3h 7m
- Temperature16m
- Linear Thermal Expansion14m
- Volume Thermal Expansion14m
- Moles and Avogadro's Number14m
- Specific Heat & Temperature Changes12m
- Latent Heat & Phase Changes16m
- Intro to Calorimetry21m
- Calorimetry with Temperature and Phase Changes15m
- Advanced Calorimetry: Equilibrium Temperature with Phase Changes9m
- Phase Diagrams, Triple Points and Critical Points6m
- Heat Transfer44m
- 21. Kinetic Theory of Ideal Gases1h 50m
- 22. The First Law of Thermodynamics1h 26m
- 23. The Second Law of Thermodynamics3h 11m
- 24. Electric Force & Field; Gauss' Law3h 42m
- 25. Electric Potential1h 51m
- 26. Capacitors & Dielectrics2h 2m
- 27. Resistors & DC Circuits3h 8m
- 28. Magnetic Fields and Forces2h 23m
- 29. Sources of Magnetic Field2h 30m
- Magnetic Field Produced by Moving Charges10m
- Magnetic Field Produced by Straight Currents27m
- Magnetic Force Between Parallel Currents12m
- Magnetic Force Between Two Moving Charges9m
- Magnetic Field Produced by Loops andSolenoids42m
- Toroidal Solenoids aka Toroids12m
- Biot-Savart Law (Calculus)18m
- Ampere's Law (Calculus)17m
- 30. Induction and Inductance3h 37m
- 31. Alternating Current2h 37m
- Alternating Voltages and Currents18m
- RMS Current and Voltage9m
- Phasors20m
- Resistors in AC Circuits9m
- Phasors for Resistors7m
- Capacitors in AC Circuits16m
- Phasors for Capacitors8m
- Inductors in AC Circuits13m
- Phasors for Inductors7m
- Impedance in AC Circuits18m
- Series LRC Circuits11m
- Resonance in Series LRC Circuits10m
- Power in AC Circuits5m
- 32. Electromagnetic Waves2h 14m
- 33. Geometric Optics2h 57m
- 34. Wave Optics1h 15m
- 35. Special Relativity2h 10m
18. Waves & Sound
Wave Functions
Struggling with Physics?
Join thousands of students who trust us to help them ace their exams!Watch the first videoVideo duration:
2mPlay a video:
Related Videos
Related Practice