Kaedah Mngajar Fizik Terbaru

ASSALAMUALAIKUM & VERY GOOD MORNING ARE YOU READY TO START OUR CLASS…?

DEMONSTRATION

ARCHI ME DES’ PRI NCI PL E

A

B

C

What is buoy ant forc e?

Buoyant force •

It is the upward force resulting from an object being wholly or partially immersed in a liquid.

•

The buoyant force acting on an object depends on: a) the volume of the object - larger object, displace larger volume of water thus experiencing a larger buoyant force. b) The density of the liquids - the higher the density of liquid, the larger the buoyant force.

beaker - OBJECT

water

beaker

beaker

water

Buoyant > weight of force object Object moves to the surface of the water

water

Buoyant force

< weight of object

Object sinks to the bottom

Buoyant force

= weight of object

Object floats or remains stationary in the water

VIDEO

Archimedes’ principle • State that for a body immersed wholly or partially in a fluid, the upward buoyant force acting on the body is equal to the weight of the fluid it displaces

25N

• initial

weight = 25N

• object is inserted into a beaker 15N

• final weight = 15N

Weight of water displaced

• loss in weight of the object = 25 - 15N = 10N •

Loss in weight

=

buoyant force

• Object is inserted into a beaker • water that is displaced by the object will flow out the side mouth and is collected in a small beaker • The weight of water = displaced

buoyant force

• Weight of object in air = W1 • Weight of object in water = W2 • Buoyant force on the object = W1- W2 • Weight of empty beaker = m1g • Weight of beaker and water displaced = m2g • Weight of water displaced = (m2-m1)g • FINDING :

W1 – W2 = (m2 – m1)g

A Freely floating object

APPLICATIONS OF ARCHIMEDES’ PRINCIPLE

SUBMARINE ballast tank – to control its position and depth from the surface of the sea. water is pumped into the balancing tank it will increase the weight of submarine. The submarine will sink The weight > buoyant force When water is remove from the balancing tank The submarine will float The weight < buoyant force

ACTIVITY • Divide into 6 group • 7 person per group TIME : 5 Minutes

HOT AIR BALLON Buoyant force • Archimedes’ principle is

applicable to the operation of the hot air balloon or gas balloon. balloons are filled with hot air which has a lower density than cold air.

weight

A hot air balloon floats and rises upwards because the buoyant force acting on it. Buoyant force > weight

SHIP • A ship can stay a float by displacing the weight of sea water equal to its own weight • The ship would sink to a certain level until its weight is equal to the buoyant force Buoyancy force

weight

BUOYANT FORCE

Buo yant > wei gh t of fo rce o bj ect Object moves to the surface of the water Buoy ant for ce

<

weig ht of o bje ct

Object sinks to the bottom

ARCHIMEDES’ PRINCIPLE

APPLICATION

Buoy ant = weig ht of for ce o bj ec t Object floats or remains stationary in the water BUOYANT FORCE = LOSS IN WEIGHT BUOYANT FORCE = WEIGHT OF FLUID DISPLACED Ship Submarines Hot air balloons

HOMEWORK • Do exercise page 99, questions 1 to 5 in the exercise book. Submit at next class.

THANK YOU