Apps-On-Physics/C2/Circular-motion/English-timed

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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.

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