Apps-On-Physics/C2/Circular-motion/English-timed
From Script | Spoken-Tutorial
| Time | Narration |
| 00:01 | Welcome to this tutorial on Circular Motion. |
| 00:06 | In this tutorial we will,
Change the position, velocity, acceleration and force with time. |
| 00:16 | Calculate angular velocity and angular acceleration. |
| 00:20 | Calculate centripetal force. |
| 00:24 | Here I am using,
Ubuntu Linux OS version 16.04 |
| 00:31 | Firefox Web Browser version 62.0.3 |
| 00:37 | To follow this tutorial learners should be familiar with Apps on Physics. |
| 00:43 | For the pre-requisite tutorials please visit this site. |
| 00:48 | Let us first define uniform circular motion. |
| 00:52 | It is a motion of an object on a circular path with a constant speed. |
| 00:58 | For example: Moon, revolves around the earth in uniform circular motion. |
| 01:05 | Use the given link to download the Apps. |
| 01:09 | I have already downloaded the Apps on Physics to my Downloads folder. |
| 01:16 | In this tutorial we will use,
Uniform Circular Motion and Model of a Carousel Apps. |
| 01:25 | Right-click on circularmotion_en.htm file. |
| 01:31 | Select the option Open With Firefox Web Browser. |
| 01:36 | Uniform Circular Motion app opens in the browser. |
| 01:41 | The interface shows a white coloured point on a circular path. |
| 01:47 | This white coloured point behaves as an object on a circular path. |
| 01:53 | Scroll down to see the complete interface. |
| 01:57 | Next to the circular path, we see a graph. |
| 02:01 | This graph shows the change in position of the object with time. |
| 02:07 | Click on the Start button. |
| 02:10 | Click on the Slow motion check-box to see the motion steadily. |
| 02:15 | The bold red vector shows the instantaneous position of the point. |
| 02:21 | The other two red vectors show the position of the point along the x and y axes. |
| 02:28 | Uncheck the Slow motion check-box. |
| 02:31 | Click on the Reset button to reset the App. |
| 02:35 | The initial position of the white point is 2 metre on x-axis and 0 metre on y-axis. |
| 02:43 | This is because the white point is on the circle that has a radius of 2 metre.
And it is pointing in the positive x-axis. |
| 02:54 | Click on the Velocity radio button. |
| 02:57 | Observe that the direction of the velocity vector is tangential to the circular path. |
| 03:04 | Click on the Start button and observe the change in direction of velocity. |
| 03:10 | Notice that the magnitude of the velocity is same but its direction changes continuously. |
| 03:17 | Observe that the representation on the y-axis has changed to velocity. |
| 03:23 | In the graph y-axis has changed from x, y to Vx , Vy. |
| 03:30 | Click on the Reset button. |
| 03:33 | Above the linear velocity the App has shown Angular velocity, denoted by omega.
The value of omega is 1.26 radians per second. |
| 03:45 | Click on the Start button. |
| 03:48 | Select Slow motion check-box. |
| 03:51 | Here the bold pink vector shows the magnitude and direction of velocity. |
| 03:57 | The other two vectors show the magnitude and direction on the x and y coordinates. |
| 04:04 | Uncheck the Slow motion check box. |
| 04:07 | We can calculate angular velocity using the formula.
ω=v/r where ω is angular velocity , v is linear velocity and r is radius of the circle |
| 04:24 | Click on the Reset button. |
| 04:27 | Change the Radius to 5 metre, |
| 04:30 | Period to 10 seconds and Mass of the object to 10 kg. |
| 04:35 | Press Enter after changing every value. |
| 04:39 | I have already calculated the value of angular velocity. |
| 04:44 | The value of angular velocity is 0.628 rad/s (radians per second). |
| 04:51 | The calculated value is same as the value shown in the App. |
| 04:56 | Click on the Acceleration radio button. |
| 04:59 | Here the blue vector shows the direction of acceleration.
This acceleration is centripetal acceleration. |
| 05:08 | The magnitude of acceleration is 1.97 metre per second square. |
| 05:15 | The direction of acceleration is towards the center of the circle. |
| 05:20 | This is the formula to calculate centripetal acceleration.
Click on Velocity radio button. |
| 05:28 | Substitute the values of angular velocity and radius into the formula. |
| 05:34 | Again click on Acceleration radio button. |
| 05:38 | Here is the calculated value of centripetal acceleration. |
| 05:43 | Observe that the calculated value is same as the one shown in the App. |
| 05:49 | Click on the Force radio button. |
| 05:52 | Note that the direction of Force vector is same as that of the Acceleration vector. |
| 05:59 | Recall from Newton's second law that force and acceleration are directly related to each other. |
| 06:06 | Click on the Start button. |
| 06:09 | Force acting on a circular field is a centripetal force. |
| 06:14 | This force is always directed towards the center. |
| 06:18 | Click on the Reset button. |
| 06:21 | Let us solve a numerical to find centripetal acceleration. |
| 06:26 | Please pause the video and read the numerical. |
| 06:30 | Then change the parameters according to the numerical. |
| 06:34 | Details about all calculations are shown in the Additional material. |
| 06:40 | For now I will calculate centripetal acceleration using the formula. |
| 06:46 | Click on Velocity radio button. |
| 06:49 | Let us substitute the values of angular velocity and radius into the formula. |
| 06:55 | The calculated value of centripetal acceleration is 3.15 metre per second square. |
| 07:02 | Click on the Acceleration radio button to compare the value. |
| 07:07 | Observe that the values are comparable. |
| 07:12 | As an assignment solve the following numericals by changing the parameters. |
| 07:19 | Let us move on to Carousel App. |
| 07:22 | To open the App right-click on carousel_en.htm file and Open With Firefox Web Browser. |
| 07:32 | Model of a Carousel App opens in the browser. |
| 07:36 | Below the name a short description about the interface is given. |
| 07:42 | Let us scroll down to see the interface. |
| 07:46 | This App shows the application of centripetal force. |
| 07:51 | Notice that eight pendulums are attached to the carousel. |
| 07:56 | Here we have four radio buttons. |
| 08:00 | By default Carousel is selected. |
| 08:04 | In the green panel we can change the values of the text-fields. |
| 08:10 | Let us change the Period to 2 seconds and press Enter. |
| 08:15 | Notice that the speed of the carousel has increased. |
| 08:20 | Due to increase in speed radius of the axis of rotation increases. |
| 08:26 | The pendulums move away from the center. |
| 08:30 | Click on the Numerical values radio button. |
| 08:34 | Here we can see different parameters that App has calculated. |
| 08:39 | The value of Velocity is 5.21 metre per second. |
| 08:45 | Note the values of Frequency, Angular velocity, and Centripetal force. |
| 08:53 | Let us increase the Period to 5 seconds. |
| 08:57 | As we increase the Period, Frequency, Angular velocity and Centripetal force have decreased. |
| 09:06 | Click on the Carousel radio button. |
| 09:09 | Observe that the carousel speed has slowed down. |
| 09:14 | Let’s change Distance between suspensions and axis of rotation to 1 metre. |
| 09:20 | Distance between suspensions and axis of rotation can be changed from 0 to 1 metre. |
| 09:27 | Observe that the size of the carousel has increased. |
| 09:31 | Let’s decrease Distance between suspensions and axis of rotation to 0.3 metre. |
| 09:38 | Note the decrease in the size of the carousel. |
| 09:42 | Change the Length of the string to 0.5 metre and observe the changes on the carousel. |
| 09:49 | Note that we can vary the Length of the string between 0 to 1 metre. |
| 09:56 | Similarly we can vary the Mass between 0.1 to 10 kg. |
| 10:03 | Click on F5 key on the keyboard to Reset the App. |
| 10:08 | Click on the Carousel with forces radio button. |
| 10:12 | Here it shows three force vectors. |
| 10:16 | Let us change Period to 2 seconds to see the vectors clearly. |
| 10:22 | Click on the Pause button. |
| 10:25 | Black vector shows the force due to the weight. |
| 10:29 | Blue vector shows the force exerted by the string |
| 10:34 | And red vector is the net force pointing inward. |
| 10:39 | To get a clear view of the vectors let us select Sketch radio button. |
| 10:45 | Here we can see a 2D view of the force vectors. |
| 10:50 | Click on Carousel radio button. |
| 10:53 | Click on the Resume button. |
| 10:56 | Let us solve a numerical by varying the parameters in the App.
Please pause the video and read the numerical. |
| 11:05 | Now, Let us change the values according to the numerical. |
| 11:11 | To calculate the centripetal force we can use the formula :
Fc= mv2/r |
| 11:20 | Click on the Numerical values radio button. |
| 11:24 | From here we will take the values of radius and velocity. |
| 11:29 | Now calculate the value of centripetal force. |
| 11:33 | Substitute the values into the formula.
We get the value of centripetal force as 4.85 Newton. |
| 11:44 | Observe that the values are comparable. |
| 11:48 | As an assignment solve the given numerical. |
| 11:53 | Let us summarise |
| 11:55 | Using these Apps we have,
Changed the position, velocity, acceleration and force with time. |
| 12:03 | Calculated angular velocity and angular acceleration.
Calculated centripetal force. |
| 12:12 | These Apps were created by Walter-fendt and his team. |
| 12:17 | The video at the following link summarizes the Spoken Tutorial project.
Please download and watch it. |
| 12:25 | The Spoken Tutorial Project team, conducts workshops and gives certificates.
For more information, please write to us. |
| 12:35 | Please post your timed queries on this forum. |
| 12:39 | Spoken Tutorial Project is funded by MHRD Government of India. |
| 12:45 | This is Himanshi Karwanje from IIT-Bombay.
Thank you for joining. |
