Your videos are clear and detailed in explaining the equation of wave :) Most of the lectures and tutors in Hong Kong just need you to remember all equations without explanations which make me confuse in using them~ Thank you for your clear explantion ;D
Hello Professor. I seem to be getting 2.21 W instead of your 21.8W. All the conversions appear correct (5 cm --> 0.05m, 5 g --> 0.005 kg, etc.), yet I am not getting the same value as you?
Isn't the tension in the string unnecessary (and wrong) for this question? If we're given the equation, then we can calculate the wave speed in the string from the angular frequency and the wave number, no? In which case, the wave speed is 500 m/s, not 141 m/s and we don't need to know the tension.
particle velocity is different with the wave velocity right? since wave velocity can be found through the eq v^2=T/linear density, how can i find particle velocity? or is there any need of finding that in some problems?
The speed of the wave is the speed at which the energy travels along the string. The speed of the particle is the speed at which a tiny section of the string moves up or down.
could you help me with a problem? The function y(x, t) (15.0 cm) cos(px 15pt), with x in meters and t in seconds, describes a wave on a taut string.What is the transverse speed for a point on the string at an instant when that point has the displacement y12.0 cm?
Edgar, First solve for t at a particular point for x and for y = 12 cm (let's say for x = 0, what will t equal when you substitute 12 cm for y) Then take the first derivative of the function. v = dy/dt and plug in the time you found in part a.
Michel van Biezen so basically y(x=0,t)= .15m*cos((Pii)(0)-15(pii)t) which will be y=.12= .15m*cos(-(Pii)t)? so (.12/.15) = cos ((pii)*t) take the inverse cosine .64= (pii) t and solve for t=.2048~t=.205 then finding the derivative of the wave equation y(x,t)=.15m*cos((pii)x-15(pii)t) y`(x,t)=-(.15)(15*(pii)* sin ((pii)x-15(pii)t) ? then i still say that x=0 velocity of a part of the string is 1.650 m/s ? but the correct answer is u=4.24 m/s
In the energy equation, it was said that particle velocity is not the same as wave velocity. But, the velocity which was found here as 141.4 m/sec. is problematic, I think...
The 141.4 m/sec is the speed at which the wave moves along the string (in the horizontal direction), note that no particle or portions of the string move in that direction. The particle velocity is the velocity at which small pieces of the string move up and down as the wave passes by.
Thank you for your kind and informative answer. Again I'd like to ask another question… If the medium is consist of porous material like hard clay soil and wave comes from left side to the right, how do soil particles move and what about the velocities of any particle and wave at the same time..?
Waves in the ground (like Earthquake waves) consist of 2 types, S-type and P-type which correspond to longitudinal waves and transverse waves. The mechanism of waves in these circumstances are somewhat different than waves on a string.
Your videos are clear and detailed in explaining the equation of wave :)
Most of the lectures and tutors in Hong Kong just need you to remember all equations without explanations which make me confuse in using them~ Thank you for your clear explantion ;D
finally found someone could save my final
@@kirkhamandy he did, I graduated :)
Your videos are extremely clear. They make physics easy to follow and understand. I watched that whole series of 21 videos.
Thank you for your great videos :D i love the way you explain so much.
Hello Professor. I seem to be getting 2.21 W instead of your 21.8W. All the conversions appear correct (5 cm --> 0.05m, 5 g --> 0.005 kg, etc.), yet I am not getting the same value as you?
thanks for your great effort, you help me alot in this chapter
Very Cool video!
Thanks.
Great series. Thanks for your help and time.
Thanks, helped me a lot!!
Isn't the tension in the string unnecessary (and wrong) for this question? If we're given the equation, then we can calculate the wave speed in the string from the angular frequency and the wave number, no? In which case, the wave speed is 500 m/s, not 141 m/s and we don't need to know the tension.
when we calculated the velocity again, can we just do v=w/k because thats the formula right
Yes, you can use that equation
particle velocity is different with the wave velocity right? since wave velocity can be found through the eq v^2=T/linear density, how can i find particle velocity? or is there any need of finding that in some problems?
is it from relation v^2 = w/k?
and what is the velocity needed in the equation of power? is it the wave velocity or the particle velocity?
The speed of the wave is the speed at which the energy travels along the string. The speed of the particle is the speed at which a tiny section of the string moves up or down.
could you help me with a problem? The function y(x, t) (15.0 cm) cos(px 15pt), with x in
meters and t in seconds, describes a wave on a taut string.What is
the transverse speed for a point on the string at an instant when
that point has the displacement y12.0 cm?
p=pii
Edgar,
First solve for t at a particular point for x and for y = 12 cm (let's say for x = 0, what will t equal when you substitute 12 cm for y)
Then take the first derivative of the function. v = dy/dt and plug in the time you found in part a.
Michel van Biezen
so basically y(x=0,t)= .15m*cos((Pii)(0)-15(pii)t) which will be y=.12= .15m*cos(-(Pii)t)? so (.12/.15) = cos ((pii)*t) take the inverse cosine .64= (pii) t and solve for t=.2048~t=.205 then finding the derivative of the wave equation y(x,t)=.15m*cos((pii)x-15(pii)t) y`(x,t)=-(.15)(15*(pii)* sin ((pii)x-15(pii)t) ? then i still say that x=0 velocity of a part of the string is 1.650 m/s ? but the correct answer is u=4.24 m/s
i forgot to mention the wave equation is in cm so in meters it will be y(x,t)= .15m*cos((pii)x-15(pii)t)
In the energy equation, it was said that particle velocity is not the same as wave velocity. But, the velocity which was found here as 141.4 m/sec. is problematic, I think...
The 141.4 m/sec is the speed at which the wave moves along the string (in the horizontal direction), note that no particle or portions of the string move in that direction. The particle velocity is the velocity at which small pieces of the string move up and down as the wave passes by.
Thank you for your kind and informative answer. Again I'd like to ask another question… If the medium is consist of porous material like hard clay soil and wave comes from left side to the right, how do soil particles move and what about the velocities of any particle and wave at the same time..?
Waves in the ground (like Earthquake waves) consist of 2 types, S-type and P-type which correspond to longitudinal waves and transverse waves. The mechanism of waves in these circumstances are somewhat different than waves on a string.