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Hooke s law phet lab

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Subido el 15 de abril de 2020 por Segismundo P.

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hi guys today I would like to talk to you about a lab that we are going to do it's a virtual lab 00:00:00
and we are going to use a tool or for that lab that is called fed that you can find on the 00:00:10
internet okay but before starting with the lab I would like to remind you any different things 00:00:17
about the Hooke's law so as you know or you should know Hooke's law describes the 00:00:25
elastic behavior of materials okay so if you have a spring like here you have a 00:00:34
spring hanging from the ceiling this is the ceiling okay when the spring is 00:00:41
without nothing hanging from it this has a length okay we are going to to mark 00:00:48
this point that the spring reaches and if we hang a mass from the spring the 00:00:55
spring is going to stretch to a different point so it's going to stretch 00:01:06
this distance okay and that distance is what we call the elongation or X so X is 00:01:11
the elongation okay well the point is that when you exert a force on the 00:01:19
screen the screen stretches and the elongation is directly proportional to 00:01:29
the force that we exert on the screen okay and we can write that with an 00:01:35
equation that's that stages that the course that we exert on the screen 00:01:44
equals a constant times the elongation of the spring okay so this constant 00:01:49
this constant depends on the spring if the spring is very weak 00:01:57
the constant is small if the spring is very strong okay the 00:02:06
constant is large right well so this is Hooke's law that states that the 00:02:26
deformation or elongation of the of the screen when you exert a force on it is 00:02:38
proportional to the force and the constant of proportionality is this K 00:02:45
that it depends on the screen it's different for each different screen okay 00:02:49
now this is if we are pulling with the force but if we hang the mass from the 00:02:55
spring the force is going to be the weight okay so in this case that we are 00:03:01
drawing here the force equals the weight of the mass okay and the weight is P 00:03:06
equals the mass times D okay now a reminder about the units that we are 00:03:18
using okay so as x is a length we use meters as f is a force we use newtons and the constant will 00:03:25
be measured in newtons per meter okay and in this case the weight is a force i remind you that the 00:03:36
weight is different from the mass so the weight is a force is a newton the mass is in kilograms 00:03:45
And the g, that is the constant of gravity, that is an acceleration, is in meters per 00:03:51
second squared. 00:03:58
This, in fact, on the Earth, on the surface of the Earth, is 9.8 meters per second squared. 00:03:59
Okay, so what we can do is use these two equations, so that we take this equation and this equation 00:04:07
and putting them together 00:04:18
we know that the force equals the weight 00:04:21
we can say that the force is the mass 00:04:24
times the g 00:04:27
which equals 00:04:28
the constant 00:04:30
times the elongation 00:04:33
so if you have 00:04:36
if the unknown is the constant 00:04:38
you can pass the x 00:04:40
to the left side 00:04:42
dividing 00:04:44
so you pass this 00:04:45
to this side dividing to isolate the constant and then in that case you 00:04:47
obtain the constant equals M times G over X and this is the first equation we 00:04:53
are going to use in the lab. Second part, imagine now that 00:05:02
the unknown is the mass so you want to isolate the mass then you will pass this 00:05:11
to this side and you will obtain that the mass equals the constants the 00:05:16
constant times the elongation over the acceleration of the gravity so we are 00:05:23
going to use these two equations in the following slides so this is equation 00:05:29
number one and this is equation number two so we go with equation number nine 00:05:36
number one sorry that says that the constant equals the mass times the 00:05:42
duration of the gravity over the elongation and then is when it appears 00:05:51
the script of the lab that we are going to do I'm going to show you the script 00:05:57
okay and I'm going to show you the tool that we are going to use for the lab and 00:06:03
And then I will come back to this board to continue with the explanation. Okay? So, let me change or switch this to the PDF that we are using. 00:06:09
okay so you will find in the instructions for the assignment that you 00:06:26
have to hand in this PDF with different with the script for the practice so you 00:06:32
have an introduction this introduction is basically what I have explained to 00:06:40
you about Hooke's law okay and then you have a picture that if you click on the 00:06:44
future you will go directly to this web page where you have this but this is 00:06:53
like they said in a lab mean that you are in the lab in the school okay so you 00:07:00
can work with the lab and take measures just by doing it quickly okay and the 00:07:06
first thing that we will do in the lab is to fill this table and try to analyze 00:07:13
what is happening okay so we have to use different masses okay and depending on 00:07:21
the mass we are going to we know that that mass is related to a to a weight 00:07:27
okay and we will analyze the displacement and try to calculate the 00:07:33
spring constant I'm going to show you what how so if we click on this okay we 00:07:39
will go to the page I'm going directly to the page where we are going to work 00:07:46
with lab okay so when you click on that page you will find this simulation okay 00:07:54
these three boxes on the right are more more advanced so we are going to use 00:08:05
only the intro box ok so you click on it and then you find this lab setting ok 00:08:11
you have two different springs we are going to use only the one on the left 00:08:22
right and we are going to set depending on the instruction for different tables 00:08:26
maybe small you see when I move the spring constant to small is very thin 00:08:34
the wire or if I move the slide to large it is very thick okay so this is a 00:08:39
stronger spring and when it's asked to be done in the center you can choose 00:08:48
maybe one two three four in the fourth point and it's something in between okay 00:08:55
so we are going to set it to small okay and then we want to mark the equilibrium 00:09:01
position so if you go to the box on the right you can click on the equilibrium 00:09:11
position and you will find the line and natural length and you will find the 00:09:16
line so this is the natural length and the equilibrium position will appear when I 00:09:23
hang a weight from the screen so imagine that I start with the 50 grams 00:09:28
weight if I hang it you see that this is the equilibrium position that is going to 00:09:37
reach but if I stop holding it it's going to oscillate okay because that's 00:09:43
when you hang something from a screen okay so if we want to stop the 00:09:51
oscillation you see that there is a red light on the left if you click on that 00:09:57
red light it's going to simulate the position when you when you stop the 00:10:03
screen and it will stop in the equilibrium position okay that's right 00:10:09
and now the point is that we distance from this point the blue line to the to 00:10:15
the dashed green line is the elongation the X and we want to measure that 00:10:21
elongation so we have a ruler so if we put the ruler with the zero on the blue 00:10:28
line you can find that this is going to be 16 and these are centimeters so 16 00:10:33
centimeters is the elongation for this first weight okay so I'm going to write 00:10:42
it down because later on we are going to complete the table so we have 16 grams 00:10:51
for the mass of 16 centimeters sorry for the mass of 50 grams okay then we're 00:10:57
going to make a second measure with this second mass is 100 grams so it's 00:11:06
oscillating again if I click on the red light I will stop the oscillation okay 00:11:16
that's it and then you see that the for the mass of 100 grams we obtain a length 00:11:23
of 32 centimeters okay well we want to express the masses in kilograms so the 00:11:30
mass 50 well I'm going back to the board to continue playing you with 00:11:40
these two measurements that we did so we come back to the board okay here we are 00:11:45
okay so we did we started with the mass of this mass okay zero point zero five 00:11:57
kilograms this is the same as the mass of 50 grams okay if you convert this 00:12:07
into kilograms right 50 grams converted into kilograms we divide by grams 00:12:13
multiplied by kilograms 1 over 1000 we get rid of the grams and we have 0.05 00:12:20
kilograms okay okay we know that the gravity is 9.8 meters per second square 00:12:30
and this is this is the same for any of the measures that we are going to make 00:12:37
because we are on the earth okay and I will let this for you okay what is the 00:12:43
weight the weight is in Newton so to calculate the weight we M times nine 00:12:49
point eight okay so we multiply these times these we obtain the weight so if 00:12:55
we do that we have point zero five times nine point eight this is zero point 00:13:03
49 newtons okay what is the displacement before the first we obtained a displacement of 16 00:13:10
centimeters but we want to have this in meters right because it's the unit in the international 00:13:24
system so we convert it so one meter is 100 centimeters we get rid of the centimeters 00:13:31
and this 0.16 meters and then we obtain the spring constant this mg the weight 00:13:37
we can write this as p over x okay so the constant is going to be p over x so the first constant 00:13:48
first constant is going to be the weight 0.49 newtons over 0.16 00:13:56
meters okay if we calculate that you see that is 3.06 newtons per meter 00:14:07
okay we will do the same for the second and if you do this the same for the 00:14:21
second you will obtain a different value. Imagine that you obtain 3.07 00:14:26
I say imagine okay so maybe you obtain a different thing okay then you have to 00:14:32
calculate the average here so you have let's say constant 1 constant 2 and 00:14:39
constant 3 and this is the average the average would be constant 1 plus 00:14:44
constant 2 plus constant 3 over 3 and when you calculate this this is the 00:14:51
average that you're going to write here okay so that's what you'll do 00:14:58
to complete and calculate the constant of the string you see that this first 00:15:04
table is when you when you set the constant to small now we are going to 00:15:11
check uh well you will have to complete all the two tables with the constant between small and 00:15:19
large and finally one with the constant to large and then if we go to the other the second table 00:15:26
that we have to complete the second table we have to calculate the mass okay so if we 00:15:35
come back to the first page you see that we have that the mass is the constant constant times the 00:15:40
elongation over the g so the mass is the constant times the elongation over the g okay we are going 00:15:49
to come back to the lab tool to check the different things that we need for this um 00:16:00
for this lab i remind you that if we set the constant too small we obtain a 3.06 newtons per 00:16:10
meter meter meter constant so we can bring this with a second where is my 00:16:17
board okay so the constant I was saying that if it's three point zero six so we 00:16:33
can bring three point zero six Newton per meter okay and then we go now to the 00:16:44
to the tool right so we go to okay and now we left this here we have three 00:16:54
different weights in here that we don't know what is the mass of those weights so 00:17:06
you check that you have the spring constant maybe in small for 00:17:12
example to use the constant of the of the spring with small and then we put 00:17:16
this weight in the spring we stop the spring and then we measure we measure 00:17:23
that is 24 okay so 24 centimeters right so then we come back to the board so we 00:17:30
said that is 24 so the displacement is 24 centimeters which if you make the 00:17:45
conversion is 0.24 meters this is 0.24 meters okay so well if you want to 00:17:54
calculate the weight the weight the weight is M times E equals K times X so 00:18:05
if you multiply this times this you are going to get to get the weight right 00:18:12
for the mass color was pink, I think. Pink for the mass. So the force or the weight 00:18:18
is going to be this times this, so 3.06 times 0.24. This is 0.73 00:18:26
Newton. We know that the gravity is 9.8 meters per second square and the mass 00:18:38
that is the last thing that we have to calculate is the weight divided by the 00:18:46
G so in this case it's going to be 0.73 Newton over 9.8 meters per 00:18:51
second square and we will obtain a mass from this point it is over 9.8 this is 00:18:59
0.075 kilograms or in grams is 75 grams okay but we have to write it in 00:19:06
kilograms so 0.075 kilograms right and it is this is the weight how you are 00:19:16
going to complete this second table okay and then finally in this group if we 00:19:25
come back to the period okay so we have the first box with the constant set to 00:19:32
small then we have a second table halfway between small and large then a 00:19:44
first string with and set to large okay this is the third and then with the one 00:19:52
that we are going to use to calculate the different masses you have the 00:20:01
equations here okay I make you aware that in English the weight we are using 00:20:04
P because it's how it appears in your book but in English we have W for weight 00:20:12
okay and finally you have to check or write choose different words in this 00:20:17
sentence to be sure that you understood the laugh as you understood the hook 00:20:27
flow and that's all guys so you have any question don't hesitate to send me a 00:20:32
message or write a question in the forum or in the virtual classroom okay so see 00:20:38
you soon bye 00:20:46
Autor/es:
Segismundo Peláez Lirola
Subido por:
Segismundo P.
Licencia:
Reconocimiento - No comercial - Compartir igual
Visualizaciones:
124
Fecha:
15 de abril de 2020 - 9:53
Visibilidad:
Público
Duración:
20′ 50″
Relación de aspecto:
1.78:1
Resolución:
1364x768 píxeles
Tamaño:
48.52 MBytes

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