Prepared By : Mr.Leon JJ Super Education3.4 APPLYING PASCALS PRINCIPLEFill in the blanks with appropriate word.1. Principle state that pressure exerted on an liquid is transmitted . to every part of the liquid. Liquid cannot be compressed, thus its pressure only can be transmitted to all direction with equal magnitude. Pascal principle states that the pressure in a liquid is transmitted equally to all directionthroughout enclosed liquidwaterPush

Exercise 3.4Pascals Principle1. By applying the Pascals Principle, draw the direction of water when the piston is pushed.

Mechanism of Hydraulic Brake1. When the brake pedal is pressed, the piston of the master cylinder applies a pressure on the brake fluid.2. This pressure is transmitted uniformly to each cylinder at the wheel, cause the pistons at the wheels to push the brake shoes to press against the surface of the brake.3. The friction between the brakes and brake shoes causes the vehicle to slow down and stop.

Q & AQ:Why is it dangerous if air bubble is trapped in the brake fluid of a braking system.

A:1. If air bubble is present in the fluid, the fluid become compressible.2. This may prevent pressure transmits through the fluid and hence causing ineffective braking effect.

Q & AQ:Why oil but not water is used as the hydraulic fluid in a hydraulic brake system?

A:1. Because the boiling point of oil is much higher than water. This can prevent the hydraulic fluid from boiling when the brake is very hot.2. Water may cause rusting in the part of the braking system

Working mechanism of a hydraulic jack.

1. When the handle is pressed down, valve A is closed whereas valve B is opened. The hydraulic fluid is forced into the large cylinder and hence pushes the piston moving upward.

2. When the handle is raised, valve B will be closed while vale A will be opened. Hydraulic fluid from the buffer tank will be suck into the small cylinder.

3. This process is repeated until the load is sufficiently lifted up.4. The large piston can be lowered down by releasing the hydraulic fluid back to the buffer tank through the release vale.

Hydraulic Systems

1. The figure below shows a hydraulic jack. The cross-sectional area of the smaller piston and the larger piston is 0.4m2 and 8m2 respectively. If the smaller piston is pushed with a force of 20N, what will be the force experience by the larger piston?20N

0.4 m28.0 m2

Solution:2. The diagram shows 3 beakers containing different liquid at same level. Arrange the diagrams according to descending order of pressure exerted at the bottom of the beaker.PQRmercuryoilwater

Answer:

Applications of Pascals Principle

1.

FIGURE 1

Figure 1 shows a person brake his car by pressing the brake pedal. The brake pedal is linked to the main piston. The main pedal transmit the brake oil through a serial of tube to operate the front and rear brake.a) (i) Name the physics principle that relates with the above situation. ..............................................................................................................................(ii) Brake will not well function if there is some air bubbles in the brake oil. Explain why?

3.5 APPLYING ARCHIMEDES PRINCIPLEFill in the blanks with appropriate word.1. Archimedes Principle states that when an object is . or immersed in a fluid, it experiences a . equal to the weight of the fluid displaced.2. For a free floating object, the buoyant force is equal to the . of the object.

The principle of Archimedes states that "The buoyant force acting on an object completely submerged in water equals the weight of the displaced water."

For submerged objects,Buoyant force = Weight of the fluid displacedFor floated objects,Buoyant force = Weight of the fluid displaced = Weight of the floated object

Exercise 3.5 Archimedes Principle1. An object of density, 40gcm-3 and mass 500g is immersed in a liquid of density 2 gcm-3. Calculatea) the volume of liquid displaced b) the mass of the liquid displacedc) the buoyant force experienced by the object (g=10ms-2)Solution:a) V=m / ==b) Let the liquid mass as m and density m=V==c) Buoyant force=Weight of liquid displaced=mg==

Application of Archimedes Principle (Plimsoll line)

Plimsoll line is a markon a vessels side indicating the maximum depth to which it may be safely immersed when loaded with cargo.

The maximum safe loading depth varies with ocean regions and seasons. In the tropics the water is warmer and therefore less dense than in temperate regions, so with the same load ships will float higher in cold regions than in the tropics. Summer and winter cause similar changes.

The density of water is determined by the salinity of water at different locations A ship will submerge deeper in freshwater than that in sea water becausethe density of freshwater is smaller. The ship can be loaded with heavier load in sea water than in freshwater.

(Hydrometer)

Hydrometer is used to measure the density of liquid. The hydrometer works on the principle that a floating object displaces a volume of liquid whose weight is equal to the buoyant force. Hydrometer will sink deeper in the less dense liquid but float higher in the denser liquid.

Design of a hydrometerCharacteristicExplanation

Lead shots are added to the baseTo lower the centre of gravity of the hydrometerSo that, hydrometer can float upright in a liquid.

Thinner and longer glass tube is usedWill give a larger scale distance and can detect small changes in the densities.

Big bulb at the base is used.So that more liquid can be displaced

For calibration, hydrometer is allowed to float in lower density and higher density liquidLiquid level in lower density and higher density is marked. The space between the two marks is divided into a number of equal divisions that give density readings.

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