I used this demonstration to start a conversation about refractive index with my IP3 kids. These hydrogels certainly generated a lot of excitement as the kids were fascinated with how invisible it becomes when placed in water.
You can get a 1000 (yes, one thousand!) of these for $1.29 at Shopee. Make sure to choose the transparent ones instead of the coloured version when checking out.
Say goodbye to the messy demonstration involving the soaking of glass in a beaker of vegetable oil or glycerin.
As promised, I am sharing another purchase made during this mid-term break for my kids.
Magdeburg hemispheres are used to demonstrate the power of atmospheric pressure. This simple demonstration kit consists of two plastic hemispheres, a rubber ring, a one-way valve, a syringe and some rubber tubing.
First, the one-way valve and the syringe are attached to the hemisphere that has a nozzle.
The two hemispheres are then placed together with the rubber ring between them. The rubber ring will serve as a seal as the hemispheres press against it when the air is pumped out.
As the syringe is pulled, the pressure inside the sphere decreases. This results in the atmospheric pressure being significantly larger than the internal pressure and thus, the hemispheres can not be pulled apart by hand.
To separate the hemispheres, remove the tubing and the hemispheres will simply fall apart as the internal pressure rises and reaches an equilibrium with atmospheric pressure.
The kit can be bought for less than S$3 here. There are other sellers that seem to offer lower prices, which I realised while doing a search for the keywords “Magdeburg Hemispheres” only after making the purchase because I was thinking it could not get any lower.
This is a hydraulic lift kit for kids that was purchased online for only S$2.10 from Shopee, with free shipping! I am not, in anyway, affiliated to this, but simply sharing about one of several fun and cheap educational sets that I bought to occupy my kids during this mid-term break.
Other than the syringe, joints and tube, the parts are mainly laser-cut from a piece of wood with a thickness of two millimetres. The instructions come with pictures for each step so even though the words are in Chinese, there is no need to read them.
This kit demonstrates Pascal’s principle which states that a pressure change in one part of a closed container is transmitted without loss to every part. Hence, the pressure change is transmitted from one syringe to another, allowing work to be done. Do not expect it to lift up very heavy weights, though as the syringes are not perfectly sealed.
I shall share about other kits that I bought for this break soon, including a $6.62 Tesla coil that I am looking forward to testing.
This is the best video I have come across so far that is used to introduce the idea of perpetual motion engines and why it violates the principle of conservation of energy.
This simulation can be used for O-level Physics, for the topic of Pressure. I created it as it was relevant to our school’s IP3 physics as well.
It demonstrates the working principle of a hydraulic press. By adjusting the cross-section areas (A) of the two cylinders, you only need a small amount of force at the narrow piston to exert a large amount of force at the wider piston. This is how, when driving, the force applied by one’s foot is enough to supply a large force to apply the brake pads on a car’s wheels.
The advantage of using GeoGebra is that one can create such simple simulations within a couple of hours and it can be readily embedded into Google Classroom, Microsoft OneNote, SLS – a wonderful tool to have during this period of full home-based learning.
While preparing for a bridging class for those JAE JC1s who did not do pure physics in O-levels, I prepared an app on using a vector triangle to “solve problems for a static point mass under the action of 3 forces for 2-dimensional cases”.
For A-level students, they can be encouraged to use either the sine rule or the cosine rule to solve for magnitudes of forces instead of scale drawing, which is often unreliable.
For students who are not familiar with these rules, here is a simple summary:
Sine Rule
If you are trying to find the length of a side while knowing only two angles and one side, use sine rule:
$$\dfrac{A}{\sin{a}}=\dfrac{B}{\sin{b}}$$
Cosine Rule
If you are trying to find the length of a side while knowing only one angle and two sides, use cosine rule: