## 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.

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>``

## 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)

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.

## 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.

## Why is Glass Transparent?

This video relates a phenomenon that we have taken for granted to the study of quantum physics (more specifically, photon absorption) and atomic structure.

## Phase Difference GeoGebra Apps

I created a series of GeoGebra apps for the JC topics of Waves and Superposition, mainly on the concept of Phase Difference. The sizes of these GeoGebra apps are optimised for embedding into SLS. When I have time, I will create detailed instructions on how to create such apps. Meanwhile, feel free to use them.

Instructions on how to embed the apps into SLS can be found at this staging environment of the SLS user guide.

Phase difference between two particles on a progressive wave. Move the particles along the wave to see the value.

Phase difference between two particles on a stationary wave. Move the particles along the wave to observe how their velocities are different or similar.

Observe velocity vectors of multiple particles on a progressive wave.

## Javascript Game to Learn How to Count Money

Trying to brush up my Javascript skills after being inspired by one of the senior specialists in ETD, I created this simple Javascript Game to teach kids how to count money using Singapore coins.

To play this game, click or press the "Play Button". Click on the coins to make up the targeted amount. Be careful as the coins will move over one another.

This is meant for children entering primary one soon so that they can learn how to pay for food at the canteen.