(3.5) Archimedes Principle(3.5) Archimedes Principle

• Bouyant Force;Bouyant Force; Upward force resulting from an

object being wholly or partially immersed in a fluid.Activity

Stated that;

for a body wholly or partially immersed in a fluid, the upward buoyant force acting on the body is equal to the weight of the fluid it displaces.

Archimedes’ principle

APPLICATION

• HYDROMETER• PLIMSOL LINE• SUBMARINE

• HOT AIR BALLOON

Shipa) The ship may sink too deeply into water

due to overloading or changes in water density when sails from one ocean to another ocean.

b) Plimsoll Line is mark on the hull of all ships to show the depths which are safe for them to navigate.

c) Normal density = BFreshwater = F or TF

Cool ocean = W

Submarine (Kapal selam)

• Submarine has ballast tank to control its position and depth below sea level.

• To float halve, water in ballast tank is driven out until the buoyant force is equal to weight of submarine.

• To fully float, water in ballast tank is driven out until the buoyant force is bigger than the weight of submarine

• To submerged, water is pumped into ballast tank until weight of submarine is bigger than buoyant force.

Hot-air Balloonsa) The weight of balloon is decrease when

its envelope is filled with gas of lower density than air (such as hydrogen or helium)

b) Total weight = weight of fabric + weight of gas in envelope

c) When buoyant force = total weight of the balloon, it remains stationary or move upward with constant velocity.

d) When buoyant force > total weight of the balloon, it accelerates upward.

HYDROMETER• Is used to compare /

determine the density of liquids.

• Lead shots is placed at the bottom to makes the hydrometer upright (tegak) in the liquid.

• In denser liquid, hydrometer will float more because volume / weight of liquid displaced is smaller than in less dense liquid.