[Science Form 5] Hydraulic Jack

Operation of a hydraulic jack

The hydraulic jack work on a system of valves,pistons and reservoirs. When the small piston is lifted, liquid rushes in from the reservoir through the open valve P. In the meantime, valve Q is closed. The cylinder connected to the small piston is filled with fluid.

When the small piston is pressed downwards, the pressure produced is transferred onto the liquid to the big piston. At the same time, valve P closes and valve Q opens.

A huge force is created depending on the area of the big piston. The, the lift on the big piston exerted is locked in position.

With another lift from the small piston, the big piston is lifted higher and higher until the desired height is reached. The tyre can then be changed. Work on the undercarriage of the car can also be carried out.

[Science Form 5] Forceful Fluidity

When a force is applied onto a liquid, the pressure created in the liquid acts in all directions. This is because when liquid is at a standstill, matter in the liquid is distributed evenly, and because of this, pressure is also distributed throughout equally. This property of liquid is captured in the hydraulic principle, which is used widely in hydraulic jacks and hydraulic brakes. The principle is based on the formula: F₁/A₁ = F₂/A₂

A small force F₁ applied on area A₁ is transferred onto a liquid and then onto on an area A₂, which subsequently produces a huge force F₂.



Note: The larger the area, the larger the force is, and thus, a greater weight can be supported.



Eg: A force of 2N is applied on area of 1m². If the area on the other end is 10m², what is the force generated at the same end?

10 times more, which is 2N x 10 = 20N



Also, pressure in liquid is seen as energy per unit volume (using the definition of work). The relationship can be easily explained by the Bernoulli's Equation.

P = Force/Area = F/A = (F x d)/(A x d) = W/V = Energy/Volume

[Science Form 5] Useful Of Microorganisms

Some microorganisms are very useful to us. Under natural conditions, they can convert raw materials into end productions that are of value to humans.

Eg:

• Bacteria Lactobacillus convert milk to yoghurt under warm conditions. They are also used in the production of cheese, beer and other fermented foods.
  
  
• Yeast carries out anaerobic respiration and produces carbon dioxide. The characteristic of yeast, called fermentation, is seen in the production of bread. The carbon dioxide raises the dough, making the bread soft.
  
  
• Bacteria act on alcohol to produce vinegar.
  
  
• In the textile industry, bacteria are mixed with plant stems. When the bacteria have decomposed the soft tissues, the fibres that are left behind are used to make cloth and ropes.
  
  
• In leather processing, bacteria produce enzyme proteases, which digest the animal tissues that are still attached to the hides. When the hides are cleaned, leather-made bags, furniture and shoes can then be manufactured.
  
  
• In the petroleum industry, bacteria are used to "clean" oil by "eating up" the impurities.

[Science Form 5] Microscopic Microbes

Microorganisms are small and can only be seen under the microscope. There are various types of microorrganisms, which can be categorised into two groups - the useful and harmful ones.

Useful microbes play an important role. They cause decomposition, synthesise medicines and make the soil fertile, etc.

Harmful microbes, on the other hand, bring diseases, and can be deadly at times.

Microorganisms can also be grouped according to their shapes, sizes, methods of reproduction, nutrition and habitat.

Below shows five different types of microorganisms.

• Bacteria
  Structural characteristic - No nuclear membrane.
  
  
• Virus
  Structural characteristic - No cytoplasm, nucleus or cell membrane.
  
  
• Fungi
  Structural characteristic - Have cell walls but no roots, stems or leaves.
  
  
• Protozoa
  Structural characteristic - Unicellular.
  
  
• Algae
  Structural characteristic - Presence of chloroplasts.