Vertical Non-Uniform Circular Motion

This is a simulation that shows the vectors of forces acting on an object rolling in a vertical loop, assuming negligible friction.

To complete the loop, the initial velocity must be sufficiently high so that contact between the object and the track is maintained. When the contact force between the object and its looping track no longer exists, the object will drop from the loop.

The following code is for embedding in SLS.

<iframe scrolling="no" title="Vertical non-uniform circular motion" src="https://www.geogebra.org/material/iframe/id/ny3jhhsp/width/640/height/480/border/888888/sfsb/true/smb/false/stb/false/stbh/false/ai/false/asb/false/sri/true/rc/false/ld/false/sdz/false/ctl/false" width="640px" height="480px" style="border:0px;"> </iframe>

Does Hydrostatic Pressure Depend on Container Shape?

The following GeoGebra app simulates a pressure sensor that measures hydrostatic pressure, calibrated to eliminate the value of atmospheric pressure.

The purpose of this simulation is to address certain misconceptions by students such as the assumption that the shape of a container affects the pressure such that the pressure differs in different containers when measured at the same depth.

Drag the dot around to compare the pressure values at the same height between both containers.

The following codes can be used to embed this into SLS.

<iframe scrolling="no" title="Hydrostatic Pressure" src="https://www.geogebra.org/material/iframe/id/wbjduxt7/width/640/height/480/border/888888/sfsb/true/smb/false/stb/false/stbh/false/ai/false/asb/false/sri/true/rc/false/ld/false/sdz/false/ctl/false" width="640px" height="480px" style="border:0px;"> </iframe>

Hydrostatic Pressure and Upthrust

This app is used to demonstrate how a spherical object with a finite volume immersed in a fluid experiences an upthrust due to the differences in pressure around it.

Given that the centre of mass remains in the same position within the fluid, as the radius increases, the pressure due to the fluid above the object decreases while the pressure below increases. This is because hydrostatic pressure at a point is proportional to the height of the fluid above it.

It can also be used to show that when the volume becomes infinitesimal, the pressure acting in all directions is equal.

The following codes can be used to embed this into SLS.

<iframe scrolling="no" title="Hydrostatic Pressure and Upthrust" src="https://www.geogebra.org/material/iframe/id/xxeyzkqq/width/640/height/480/border/888888/sfsb/true/smb/false/stb/false/stbh/false/ai/false/asb/false/sri/false/rc/false/ld/false/sdz/false/ctl/false" width="640px" height="480px" style="border:0px;"> </iframe>

IP3-02-Kinematics

Graphical relationship between acceleration, velocity and displacement

I created the following GeoGebra app to illustrate the relationships between the physical quantities acceleration, velocity and displacement.

  1. Modify the acceleration graph using the two green dots. Notice how the velocity and displacement graphs would change.
  2. You can set the initial values of velocity and displacement using the orange and red dots respectively.
  3. Press "Play" to observe how the object moves. Note: the animation takes place in slow-motion, not in real time.
  4. Uncheck any of the graphs to hide them.

Here are some learning activities you can try out.

  1. Predict the displacement-time graph, following these steps:
    1. Uncheck the displacement-time graph.
    2. Move the two dots on the acceleration-time graph to zero acceleration.
    3. Move the initial velocity to - 10 m s-1.
    4. Predict how the displacement-time graph will look like.
  2. Predict/describe the movement of the object.
    1. Set the dots for acceleration to remain constant for a period of 4 seconds at - 10 m s-2, initial velocity at 20 m s-1, and initial displacement at 0 m.
    2. Predict how the object will move, taking the upward direction as positive.
    3. Press "Play" to verify your answers.

For embedding into SLS:

<iframe scrolling="no" title="Acceleration, velocity and displacement graphs" src="https://www.geogebra.org/material/iframe/id/qpxcs6vb/width/638/height/478/border/888888/sfsb/true/smb/false/stb/false/stbh/false/ai/false/asb/false/sri/true/rc/false/ld/false/sdz/false/ctl/false" width="638px" height="478px" style="border:0px;"> </iframe>

Area under velocity-time graph

Noise-cancelling AirPod Pro

The recently launched Apple AirPod Pro presents a wonderful opportunity to relate an A-level concept to a real-world example - how noise-cancelling earphones work.

Apple's website explained it in layman terms that seem to make sense. Let your students attempt to do a better job of explaining how destructive interference of waves is applied.

I probably won't spend SGD379 on it though.

Micro:bit Line-Following Robot

I was looking for an extension to the Micro:bit Go set that I bought a while back and came across a robot set that is currently on sale. This set comes with most of the sensors a typical line following or obstacle avoiding robot needs. Currently, it is being sold at a fraction of the price of other similar Micro:bit robots, and is far cheaper than sets such as the Lego EV3.

After unpacking it earlier this evening after work, I managed to put together the parts by following the instructions, which were quite clear.

  1. Micro:bit Go (S$30 on Lazada)
  2. Yahboom Micro:bit Robot (selling for S$49.68 only at Lazada)
Before assembly
Microbit Line Following Robot
Microbit Line Following Robot

To program the robot using Micro:bit's Makecode, which is a block programming interface that is very similar to Scratch, you will need to download the Yahboom blocks by selecting Extensions from the Advanced menu.

Enter the following URL into the search bar: https://github.com/lzty634158/yahboom_mbit_en

You will then see the library of new blocks including those meant for the robot below:

A few simple lines of code are all that is needed for the light sensors to keep tracking a black line by turning whenever one of the sensors detect white while the other detects black.

After programming the robot, download the hex file into the Microbit and the robot is good to go.

one-north Festival 2019

https://www.seriouslyscience.sg/one-north-Festival/Overview

Happening now from 13-14 Sept 2019 at one-north.

My colleagues and I took the opportunity to visit the exhibitions during lunch time today. I learnt about 3M's solar films and retroreflection material, I^2R's speech-to-text recognition app with code switching capabilities (i.e. the app is able to transcribe English-Chinese mixed sentences) and cell-based prawn meat from https://shiokmeats.com/, among other things.

There was also an informative booth on Project Wolbachia (where male aedes mosquitoes infected with Wolbachia bacteria are released into the wild to control the population). I learnt that they could separate the male from the females at the pupal stage because male pupals are larger and got to stick my hand in a box full of male Wolbachia-Aedes mosquitoes.

Very hands-on booth on Project Wolbachia.
Looking forward to a future where meat is grown in labs so as to reduce animal suffering

Do check out the apps developed by the Bioinformatics Institute that can be used for science experiments or related applications.

Iconic Voices from MIT: Opening a New Window into the Universe with Dr Nergis Mavalvala

This is a free public lecture by Dr Nergis Mavalvala (an astrophysicist from MIT) on how her team detected gravitational waves generated from colliding black holes and neutron stars at the Laser Interferometer Gravitational-wave Observatory (LIGO).  Held on this coming Friday 26 Jul 2019 from 5 to 6 pm, the venue is at the Singapore University of Technology and Design (SUTD)'s Auditorium, along 8 Somapah Road, Singapore 487372.

Click here to sign up.