National Day – Floating Platform @ Marina Bay

In the past, the National Day Parade was always held in the National Stadium. Besides being the venue for the National Day Parade 18 times, the stadium that could hold a capacity of 55, 000 people has also played host to many sporting, cultural, entertainment and national events, such as the Southeast Asian Games, Singapore Armed Forces Day, Singapore Youth Festival Opening Ceremony and the finals of the 2004 Tiger Cup.

However, the National Stadium was officially closed on 30 June 2007 and is scheduled to be demolished to make way for the Singapore Sports Hub which is expected to open in 2014. Hence, the Float @ Marina Bay was built as a temporary stadium for the next 5 years in lieu of the closure of the National Stadium.

The Float @ Marina Bay also known as the Marina Bay Floating Platform is the world’s largest floating stage. It is located on the waters of the Marina Reservior. Made entirely of steel, the floating platform on Marina Bay measures 120 m by 83 m and can bear up to 1,070 tonnes, equivalent to the total weight of 9,000 people, 200 tonnes of stage props and three 30-tonne military vehicles. The gallery at the stadium has a seating capacity of 30,000 people.

The density of an object is defined as its mass per unit volume.

Mass: amount of matter contained in an object and is commonly measured in kilograms (kg).

Volume: amount of space taken up by the matter and is commonly expressed in cubic meters (m³).

Units used to express density : kilogram per cubic meter (kg/m³) or grams per cubic centimeter (g/cm³).

Note: 1 g/cm³ = 1000 kg/m³

Different objects have different density.

 

                                        Densities of common substances

The ability of an object to "float" when it is placed in a fluid is called buoyant force, and is related to density. If an object is less dense than the fluid in which it is placed, it will float. If it is denser than the fluid, it will sink.

A steel ship will float even though it may be made of steel (which is much denser than water), because it encloses a volume of air (which is much less dense than water), and the resulting shape results in a total density that is less than that of the water. The same principle applies to the floating platform. Although it is made of steel, it has a large surface area and encloses a volume of air which makes it less dense than water. Thus, the platform could support a weight of 1, 070 tonnes without sinking.

National Day - Fireworks

Fireworks (devices) take many forms to produce the four primary effects: noise, light, smoke, and floating materials (confetti for example). They may be designed to burn with colored flames and sparks including red, orange, yellow, green, blue, purple, and silver.

Colors in fireworks are usually generated by pyrotechnic stars—usually just called stars—which produce intense light when ignited. Stars contain five basic types of ingredients.

·         A fuel which allows the star to burn

·         An oxidizer—a compound which produces (usually) oxygen to support the combustion of the fuel

·         Color-producing chemicals

·         A binder which holds the pellet together.

·         A chlorine donor which provides chlorine to strengthen the color of the flame. Sometimes the oxidizer can serve this purpose.

 

Reference of chemicals used in fireworks industry

The color of a compound in a firework will be the same as its color in a flame test.

Symbol	Name	Fireworks Usage
Al	Aluminum	Aluminum is used to produce silver and white flames and sparks. It is a common component of sparklers.
Ba	Barium	Barium is used to create green colors in fireworks, and it can also help stabilize other volatile elements.
C	Carbon	Carbon is one of the main components of black powder, which is used as a propellent in fireworks. Carbon provides the fuel for a firework. Common forms include carbon black, sugar, or starch.
Ca	Calcium	Calcium is used to deepen firework colors. Calcium salts produce orange fireworks.
Cl	Chlorine	Chlorine is an important component of many oxidizers in fireworks. Several of the metal salts that produce colors contain chlorine.
Cs	Caesium	Cesium compounds help to oxidize firework mixtures. Cesium compounds produce an indigo color in fireworks.
Cu	Copper	Copper produces blue-green colors in fireworks and halides of copper are use to make shades of blue.
Fe	Iron	Iron is used to produce sparks. The heat of the metal determines the color of the sparks.
K	Potassium	Potassium compounds help to oxidize firework mixtures. Potassium nitrate, potassium chlorate, and potassium perchlorate are all important oxidizers. The potassium content can impart a violet-pink color to the sparks.
Li	Lithium	Lithium is a metal that is used to impart a red color to fireworks. Lithium carbonate, in particular, is a common colorant.
Mg	Magnesium	Magnesium burns a very bright white, so it is used to add white sparks or improve the overall brilliance of a firework.
Na	Sodium	Sodium imparts a yellow color to fireworks, however, the color is often so bright that it frequently masks other, less intense colors.
O	Oxygen	Fireworks include oxidizers, which are substances that produce oxygen in order for burning to occur. The oxidizers are usually nitrates, chlorates, or perchlorates. Sometimes the same substance is used to provide oxygen and color.
P	Phosphorus	Phosphorus burns spontaneously in air and is also responsible for some glow in the dark effects. It may be a component of a firework's fuel.
Ra	Radium	Radium would create intense green colors in fireworks, but it is far too hazardous to use.
Rb	Rubidium	Rubidium compounds help to oxidize firework mixtures. Rubidium compounds produce a violet-red color in fireworks.
S	Sulfur	Sulfur is a component of black powder, and as such, it is found in a firework's propellant/fuel.
Sb	Antimony	Antimony is used to create firework glitter effects.
Sr	Strontium	Strontium salts impart a red color to fireworks. Strontium compounds are also important for stabilizing fireworks mixtures.
Ti	Titanium	Titanium metal can be burned as powder or flakes to produce silver sparks.
Zn	Zinc	Zinc is a bluish white metal that is used to create smoke effects for fireworks and other pyrotechnic devices.

Fireworks produce smoke and dust that may contain residues of heavy metals, sulfur-coal compounds and some low concentration toxic chemicals. These by-products of fireworks combustion will vary depending on the mix of ingredients of a particular firework.

Pollutants from fireworks raise concerns because of potential health risks associated with hazardous by-products. For most people the effects of exposure to low levels of toxins from many sources over long periods are unknown. For persons with asthma or multiple chemical sensitivity the smoke from fireworks may aggravate existing health problems.

Improper use of fireworks may be dangerous, both to the person operating them (risks of burns and wounds) and to bystanders; in addition, they may start fires after landing on flammable material. For this reason, the use of fireworks is generally legally restricted.

Racial Harmony Day - Sepak Takraw

Have you ever played Sepak Takraw? Have you ever wondered how you could control the path of the rattan ball better? Is there any science behind the path that the rattan ball takes after you've kicked it?

The answer is YES!!! Projectile motion is involved while playing the Sepak Takraw. If you aspire to be a professional Sepak Takraw player, this post is a MUST READ!!

Sepak Takraw also known as kick volleyball is a sport native to the Malay-Thai Peninsula. It is a popular sport in South-east Asia. The difference between sepak takraw and the similar sport of volleyball is in its use of a rattan ball and players are allowed only to use their feet, knee, chest and head to touch the ball.

The physics behind Sepak Takraw is that when the rattan ball is kicked, the ball will follow a parabolic path as there is both a vertical and horizontal component of the velocity as shown in the video and pictures below:

 

The horizontal projectile motion is always analyzed separately from the vertical projectile motion.

Let x denote the horizontal components of the projectile motion.

Let y denote the vertical component of the projectile motion.

Assuming the ball is kicked with an initial velocity of magnitude u in a direction at angle A above the horizontal as shown below:

The formula of the various horizontal and vertical projectile motions is as shown below:

Horizontal projectile motion	Vertical projectile motion
Initial velocity = u cos A	Initial velocity = u sin A
Acceleration, a = 0	Acceleration, a = - g (g = gravity)
Time taken = t	Time taken = t
Distance moved, x = ut cos A + ½ at2 = ut cos A	Distance moved, y = (ut sin A) + ½ at2 = (ut sin A) - ½ gt2
Final speed vx = u cos A + at = u cos A	Final speed vy = (u sin A) + at = (u sin A) - gt

The horizontal velocity will always remain constant while the vertical velocity will decrease steadily at a rate of 10 m/s² due to the gravity.

Applying Phytire Theroem,  after time, t:

Hence, it can be seen that the initial velocity u and the angle A at which the rattan ball is kicked is very important for the subsequent path of the rattan ball. The following video shows the path of the rattan ball when it is kicked at various angle A.

Applet

http://galileo.phys.virginia.edu/classes/109N/more_stuff/Applets/ProjectileMotion/jarapplet.html

Besides Sepak Takraw, there are also many other sports that apply the principle of projectile motion.