• Bouyant Force;
Upward force resulting from an object
being wholly or partially immersed in a
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.
• PLIMSOL LINE
• HOT AIR BALLOON
a) The ship may sink too deeply into water
due to overloading or changes in water
density when sails from one ocean to
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 = B
= 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.
a) The weight of balloon is decrease when
its envelope is filled with gas of lower
density than air (such as hydrogen or
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.
• Is used to compare /
determine the density of
• Lead shots is placed at
the bottom to makes the
(tegak) in the liquid.
• In denser liquid,
hydrometer will float more
because volume / weight
of liquid displaced is
smaller than in less