Constructive VS Destructive Interference

When the waves strike other waves, instead of reflect they combine to each other. There are two types of interferences, one is constructive interferences and one is destructive interferences. The amplitudes of two waves are same direction (both waves is positive or both negative) so we will combine the two waves together by adding them together is called Constructive interferences. However, if the two amplitudes have opposite direction, we combine those two waves by subtracting. This is called destructive interference. And Constructive interference will make a sound louder while destructive interference will make a sound quieter.

Different Types of Energy

Chemical potential energy：

Chemical potential energy is a form of potential energy related to the structural arrangement of atoms or molecules. Chemical energy stored in the chemical bonds of matter. Chemical reaction is transformed by chemical energy of chemical substance.

Gravitation potential energy:

Gravitational potential energy is stored in the gravitational field, due to its height in an area above the surface of the Earth, where the force of gravity can act on it to make it fall.




Elastic potential energy:


Elastic potential energy is the energy stored by the bending, stretching or compressing, stored deformation of an elastic object, such as the stretching of a spring.




Mechanical potential energy:

Mechanical energy is the energy that is an object due to its motion or due to its position. Mechanical energy can be either kinetic energy (energy of motion) or potential energy (stored energy of position). Objects have mechanical energy if they are in motion or if they are at some position relative to a zero potential energy position.




Thermal energy:


Thermal energy is the energy that makes objects hot. It is a form of kinetic energy at the molecular level, the movements of atoms and molecules. For example, Hot water has more kinetic energy then cold water.




Sound energy:


Sound energy travel through a specific medium, the energy produced by sound vibrations. Sound vibrations because waves of pressure which lead to some level of compression. Sound energy is a form of mechanical energy; is not related to any chemical change, but is purely related to the pressure its vibrations cause.

CANNON !!

Cannon uses gunpowder or other explosive-based propellants to launch a projectile. The Jaivana cannon is the world's biggest wheeled cannon ever made. It is located in India. It was built in 1720, Jaivan rests on a high 4 wheeled carriage. The front wheels are 2.74 m in diameter and the rear wheels are 1.37 m in diameter. The length of the barrel of the cannon is 20 feet 2 inches and it weighs 50 tons. The circumference near the tip of the barrel is 7 feet 4 inches and that of the rear is 9 feet 4 inches. The diameter of the bore of the barrel is 11 inches and the thickness of the barrel at the tip is 8-1/2 inches. The thickness gradually increases towards the rear of the barrel. A 776 mm long elevating screw was used for raising and lowering the barrel. Reportedly, it took four elephants to swivel it around on its axis. The cannon uses about 100 kg of gun powder fired a shot ball weighing 50 kg. The uses and range of the cannon and cannonballs vary over different sources. Some say the Jaivana Cannon was only fired once by the Maharajah Jai Singh, as a test-fire in 1720. Others say that it was fired many times, indicated by the fire marks on the inside of the barrel. The most exaggerated was it had a range of 40 km with the Maharajah's test fire; other sources say it is 35, 22 and 11 km.

4 NEWTONS PROMBLEMS !!

Formulas：

F=ma   Fk=μkFn   Fs=μsFn

Equilibrium

There is no force when the force is balanced.

Assumptions:

-          no air resistance

-          no friction

-          a=0 ( ax=0 and ay=0 )

-          set positive axis

-          break down in to x and y components

-          Free Body Diagram

-          T1x=T2x

Inclines (Static) / Incline (Kinetic)

The object in on an incline surface, one is static has no acceleration and another one is kinetic with acceleration.

Inclines (Static) Assumptions:

-          no air resistance

-          FN  perpendicular to the surface

-          positive axis is the direction of acceleration

-          no acceleration

-          break down in to x and y components

-          Free Body Diagram

-          Fgx-f=0

-          FN-Fgy=0

Inclines (Kinetic)
Assumptions:

-          no air resistance

-          FN  perpendicular to the surface

-          positive axis is the direction of acceleration

-          break down in to x and y components

-          acceleration does not equal to zero

-          Free Body Diagram

-          FN-Fgy=0

-          Fgx-f=ma

Pulley

A pulley has two mass one is going up and one is going down, is used to change the direction of an applied force, the acceleration are the same.

Assumption:

-          pulley is frictionless

-          rope frictionless

-          no air resistance

-          Positive axis is the position of the

-          2 system, 2 Free Body Diagrams

-          T1=T2

-          Acceleration of the system is the same ay1 = ay2

-          break down in to x and y components acceleration

Trains

We assume the train as a whole.

Assumption

-          positive axis is the direction of acceleration

-          acceleration is constant

-          no air resistance

-          acceleration of the system is the same

-          ay = 0

-          3 Free Body Diagrams
-          T1y-T2y-Fg= 0

Projectile Motion

   Projectile motion is a two dimensional motions with constant acceleration.  The motion of an object projected into the air at an angle. For examples, when you are kinking a soccer ball, throwing a baseball, or a long jumping. When a projectile is an object upon which the only force acting is gravity.

There is no acceleration in Vx, gravity is the acceleration in Vy.

         

             Path of a projectile projected at an angle with horizontal direction.

Component projectile velocities in x and y direction,the Vx stays the same and moving at constant speed.

Four Types of Projectile Promblems:

Type 1:

Type 2:

Type 3:

Type 4:

Physics Behind Roller Coaster

Gravity is the driving force of a roller coaster. The train is pulled to the top by gaining potential, or stored energy. As the train is pulled to the top, the train is released from the top of the lift hill; it is the acceleration due to gravity that brings it back to the beginning, its velocity increases. This causes the train to gain kinetic energy, which is the energy of motion. The faster the train moves, the more kinetic energy the train gains. The train begins to climb the next hill and the speed start to decreases.

                                                
                                        The initial hill is the steepest in the entire ride.

Behemoth is my favorite roller coaster, it clear shows the gravity and potential energy and also velocity and kinetic energy.

Vector Addition

Two or more vector can be added together to determine the result, there is no minus sign in those in vector addition, if the vector going to the opposite direction, for example, North and South, we use North + South instead of North + (-North).

We use Pythagorean Theorem and head to tail method to determining the magnitude and direction of adding two or more vectors.

 

 

We use trigonometry to determine a vector's direction

                                                                   1 km [N 45°E]         

                                                         One kilometer 45°east of north