Waves

Longitudinal Waves

Transverse Waves

Wavefront

Circular or spherical Wave

Flat or plane Wave

Impulse and Impulsive Force

Definition

Impulsive force - rate of change of momentum in a collision/explosion
Impulse - change of momentum

Ft=mv-mu

" The time impact must be increase to reduce the impulsive force acted on the object"
  ~Zul~

Momentum

Definition

p = mv

+ product of mass time velocity

Elastic collision

Total momentum before collision = Total momentum after collision

Inelastic collision

Total momentum before collision = Total momentum after collision

Inertia

Definition

The tendency of an object to move with constant velocity or remain at rest unless external force is applied

+ The larger the mass, the bigger the inertia

" Inertia is a property, not a quantity. Therefore, it is wrong to state bigger or smaller inertia.
  However, it is generally accepted that bigger mass have bigger inertia."
  ~Zul~
 

Bernoulli's Principle

Definition

High speed flow of a fluid is associated with low pressure and low-speed flow is associated with high pressure
High speed = pressure low
Low speed = pressure high

Application

Aerofoil

+ wing of airplane is the shape of an aerofoil
+ such shape causes air to flow more rapidly over its surface than its lower one
+ top surface = low pressure
+ bottom = high pressure
+ the difference in pressure = upward resultant force 
+ lifts the aircraft in flight
+ an aerofoil in an inverted position = downward pressure

Carburetors

+ air is passed through a venturi tube to increase its speed = decrease the pressure
+ low pressure air is routed over a tube leading to a fuel tank
+ low pressure = suck the fuel into airflow

Bunsen Burner

+ gas comes at high speed = low pressure
+ atmospheric pressure push air into the hole
+ air and gas mixture produces blue flame

Insecticide Sprayers

+ when the plunger is pushed quickly air inside the cylinder is forced out the narrow outlet at high speed
+ a low pressure is created at the nozzle
+ atmospheric pressure pushes the insecticide out of the metal tube
+ the insecticide is carried by the air jet coming out of the outlet

Archimedes' Principle

Definition

Object that is partially or totally submerged in a fluid will experience a buoyant force equal to the weight of the fluid of the object displaced

Application

+ submarine floats or submerges by changing its buoyancy
+ ballast tanks control its buoyancy
+ when ballast tank is full of air, submarine is less dense than the water(float)
+ to submerge, submarine opens the vents on top of the ballast tanks
+ seawater fills the ballast tanks and forces air out of the vents
+ submarine is now dense than the water(sink)
+ the depth can be controlled by adjusting the water to air ratio in ballast tanks
+ to make submarine rise, compressed air is blown into ballast tanks forcing the seawater out
+ submarine becomes less dense(rise)

Hydrometers

+ used to determine density of liquid
+ thin glass tube closed at both ends
+ if the density of liquid is greater, the object floats higher
+ if hydrometer floats deeper, the liquid has low density

Hot-air Balloons

+ inside air balloon is heated by external burner
+ hot air < cold air = balloon floats
+ buoyancy of balloon controlled by the burner

Pascal's Principle

Definition

Pressure exerted on an enclosed incompressible fluid is transmitted equally undiminished to every part of the liquid

Hydraulic System

Hydraulic Brake

+ small force is exerted on the small piston
+ force is transmitted to bigger pistons attached to the brakes
+ small force applied will be transmitted and turned into a huge force on the brakes
+ bigger pistons push the brake pads against the spinning disc
+ wheel becomes slower