Difference between revisions of "PhET/C3/Pendulum-Lab/English-timed"

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|| The '''Spoken Tutorial Project''' team, conducts workshops using spoken tutorials and  
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gives certificates on passing online tests.  
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Latest revision as of 12:17, 10 October 2019

Time Narration
00:01 Welcome to the Spoken Tutorial on Pendulum Lab simulation.
00:06 In this tutorial we will demonstrate, Pendulum Lab PhET simulation.
00:13 Here I am using: Ubuntu Linux OS version 16.04
00:20 Java version 1.8.0
00:25 Firefox web browser version 62.0.3
00:31 To follow this tutorial, Learner should be familiar with topics in high school physics.
00:38 Using this simulation, we will, Describe simple harmonic motion.
00:44 Demonstrate the oscillations of a pendulum.
00:48 Investigate the factors that affect the oscillations of a pendulum.
00:54 Explain Conservation of energy during motion of the pendulum.
01:00 Demonstrate the oscillations for a pair of pendulums.
01:05 Demonstrate the oscillations of a pendulum on other celestial bodies.
01:11 A simple pendulum has a fixed string attached to a bob.
01:17 Now we will define simple harmonic motion.
01:21 Simple harmonic motion arises when the force on the oscillating body is directly proportional to its displacement from its mean position.
01:33 That is F α -x .
01:38 In SHM there is a continuous interchange of kinetic and potential energies.
01:45 Here, mechanical energy is conserved.
01:49 Use the given link to download the simulation.
01:53 I have already downloaded the simulation to my Downloads folder.
01:58 Right click on pendulum-lab_en.html file.
02:02 Select the option Open with Firefox Web Browser.
02:07 Pendulum Lab simulation opens.
02:11 In the Pendulum lab simulation, we have three screens Intro ,Energy ,Lab
02:21 Click on Intro screen to open it.
02:25 In this screen we have, A blue coloured pendulum.
02:30 A Protractor to show the changes in the angle of the pendulum.
02:35 A ruler to measure the distance from the fixed point to the centre of mass.
02:41 Length and Mass sliders to change the length and mass of the pendulum.
02:47 Gravity and Friction sliders to change gravity and friction.
02:53 At the bottom left corner of the screen we have grey coloured box.
02:58 It has the following check boxes.
03:02 A Ruler ,A Stopwatch and A Period Trace.
03:09 At the bottom of the screen we have, A Pendulum and a Pair of pendulum buttons.
03:16 Stop button to stop the oscillations of the pendulum.
03:21 Play/Pause and Step buttons.
03:25 Normal or Slow radio buttons to change animation speed.
03:30 And a Reset button to reset the simulation.
03:35 For the pendulum, reference line on the bob is the centre of mass.
03:41 Pendulum’s angle can be changed from 180 to -180 degrees.
03:47 Drag the pendulum to a particular angle say 30 degrees and allow to oscillate.
03:55 Here, default length of pendulum is 0.70 m.
04:01 Now click and drag the Length slider towards left till 0.30 m.
04:08 Observe that as we decrease the length, pendulum oscillates faster.
04:14 Drag it back to 0.70 m.
04:19 The default mass of pendulum is 1 kg.
04:24 Click and drag the mass slider towards left till 0.50 kg.
04:32 Observe that as we change the mass, it does not affect the oscillations of the pendulum.
04:39 Note that Friction slider is at None.
04:43 Now click and drag the Friction slider towards Lots.
04:48 Observe that the oscillations of the pendulum slow down.
04:53 After sometime pendulum stops oscillating.
04:57 This is due to increase in friction, as friction damps the oscillations of the pendulum.
05:04 Click on Reset button to reset the simulation.
05:09 Now let us measure time for 10 oscillations at different lengths.
05:16 We will make a tabular column, to show length and time for 10 oscillations of a pendulum.
05:24 Next select the Stop watch to record the time for 10 oscillations.
05:31 We will count 10 oscillations for length 0.70 m.
05:37 Click and drag the pendulum at an angle of 30 degrees to count number of oscillations.
05:44 Now we will count the 10 oscillations.
05:47 one, two, three, four, five, six, seven, eight, nine, ten.
06:05 Note the value in the table.
06:09 To find the mean time taken for 10 oscillations, we need to measure the time for 0.70 m again.
06:19 Click on Reset button of the Stop watch to take the count of next 10 oscillations.
06:26 Click on Stop button to stop the oscillations.
06:31 Change the length to 0.60 m.
06:35 Follow the same steps to count 10 oscillations for length 0.60 m.
06:43 Here I have already taken the observations for two different lengths.
06:49 As an assignment, Change the length of the pendulum to 0.50 m, 0.40 m and 0.30 m.
07:01 Count for 10 oscillations.
07:05 Note down the time.
07:08 Next we will move on to Energy screen.
07:12 Click on Energy screen button at the bottom of the interface.
07:18 In this screen we will explain how energy is conserved during the oscillations of the pendulum.
07:25 Energy screen has almost same tools as that for Intro screen except for the Energy Graph.
07:34 Click and drag the pendulum to 60 degrees and allow it to oscillate.
07:40 Observe the graph.
07:42 From the drop down below Gravity select Jupiter.
07:47 Observe the change in graph.
07:50 Click on the Slow radio button to see the change in graph during the oscillations of the pendulum.
07:58 Here, we observe that at the extreme positions the potential energy is maximum.
08:05 At the mean position the kinetic energy is maximum.
08:10 Therefore, the total mechanical energy is conserved during the motion.
08:16 Click on the Normal radio button.
08:19 Now we will see the effect of friction in the graph.
08:23 Click and drag the Friction slider towards Lots.
08:28 Observe that due to increase in friction there is sudden increase in thermal energy.
08:35 After sometime total mechanical energy equals thermal energy.
08:41 This is because friction damps oscillations of the pendulum.
08:47 Now we will move to Lab screen.
08:50 In this screen we have the same tools that are included in previous screens.
08:57 Additionally we have velocity and Acceleration check boxes at the top left corner.
09:04 And Period Timer instead of Period Trace.
09:08 Select the pair of pendulums.
09:11 Here, we can see that on the top right corner, there are two lengths and two mass sliders.
09:19 The default length of second pendulum is 1 m.
09:24 Default mass is 0.50 kg.
09:29 Drag the blue pendulum to 60 degrees and allow it to oscillate.
09:35 Similarly, drag the red pendulum.
09:40 Note that green colour is for Velocity vector.
09:44 And yellow is for Acceleration.
09:47 Select Velocity check box.
09:50 Select the Slow radio button to observe the velocity vector carefully.
09:56 Here, we observe that velocity is maximum at its mean position.
10:01 It decreases at the extreme positions.
10:06 This is due to maximum kinetic energy at the mean position.
10:12 Similarly, let us select Acceleration vector and observe the change in acceleration.
10:20 As an assignment, Explain why acceleration is maximum at extreme positions?
10:29 Click on Reset button to reset the simulation.
10:34 Using the pendulum, we will compare calculated and measured Time period for different lengths.
10:42 Let us make a tabular column for Length L, Time period T (Calculated) and Time period T (Measured).
10:51 We can calculate the time period using formula: T=2π√(l/g)
11:00 Where ‘l’ is length and ‘g’ is acceleration due to gravity.
11:06 Value of g = 9.81 m/s^2.
11:13 Select Period Timer.
11:16 On the right side of the screen a Period Timer appears.
11:21 Note down 0.70 m in the length column.
11:26 Here I have already calculated the time period using the formula.
11:32 We will measure the time period from the simulation.
11:38 Now click and drag the pendulum to 40 degrees.
11:43 Click on the start button of the Period Timer.
11:47 Value for time period appears on the screen.
11:51 Note the time period in the measured column.
11:55 Now change the length to 0.60 m.
12:00 Again click on the Period Timer.
12:06 Note the value in the table.
12:09 As an assignment, Change the lengths of the pendulum to 0.50 m, 0.40 m, and 0.30 m.
12:21 Note down the measured Time period.
12:24 Calculate the time period using the formula.
12:27 Compare the calculated and measured time period values.
12:34 Next Reset the simulation.
12:37 Drag the pendulum to 30 degrees to oscillate.
12:41 Note that acceleration due to gravity on Earth is 9.81 meter per second square.
12:49 Now select Jupiter from the drop down list.
12:53 Observe the change in oscillations of the pendulum.
12:58 Note that value of acceleration due to gravity on Jupiter is more than that on Earth.
13:07 As an assignment, Observe the oscillations on other celestial bodies.
13:14 Let us summarise
13:16 In this tutorial, we have demonstrated, How to use Pendulum lab PhET simulation.
13:24 Using this simulation, we have, Described simple harmonic motion.
13:30 Demonstrated oscillations of a pendulum.
13:34 Investigated the factors that affect the oscillations of a pendulum.
13:40 Demonstrated how energy is conserved during oscillations.
13:45 Demonstrated the oscillations of a pair of pendulums.
13:50 Observed the oscillations on other celestial bodies.
13:55 The video at the following link summarizes the Spoken Tutorial project.
14:01 Please download and watch it.
14:04 The Spoken Tutorial Project team, conducts workshops using spoken tutorials and gives certificates on passing online tests.
14:14 For more details, please write to us.
14:18 Please post your timed queries in this forum.
14:22 This project is partially funded by Pandit Madan Mohan Malaviya National Mission on Teachers and Teaching.
14:30 Spoken Tutorial Project is funded by NMEICT, MHRD, Government of India.
14:37 More information on this mission is available at this link.
14:42 This is Himanshi Karwanje from IIT-Bombay.
14:46 Thank you for joining.

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