FINAL EXAM

1.      Kinetic Energy

Kinetic energy is energy that a motion object. Energy that objects similar to the work done by the force acting on the object to change the object from being still to a state of motion.

The kinetic energy there are 2, that are :

- Translational kinetic energy is the energy owned by objects that motion on a straight track
- Kinetic rotational energy is the energy owned by objects that do rotational motion.

          Okay I observed a door in my house, when we pushed open the door, the door also rotates or rotating on an axis. The hinge that connects the door to the wall serves as the axis of rotation. and when the door is rotates door edges motion faster or more speed. Instead part door near the hinges to motion more slowly or less velocity. So when an object rotates, the velocity (v) of each particle is different, depending on the distance from the axis of rotation. Because each particle has a mass (m) and velocity (v) then we can say that when a rigid rotates, the particles that make up all matter has a kinetic energy of translational kinetic energy, and the total kinetic energy of all the particles that make the same rigid kinetic energy of rigid. Mathematically it can be written :

And in my observation happens rotational kinetic energy. Unit of kinetic energy is the joule, the same as other forms of energy. The kinetic energy is usually dependent on the mass and velocity, but the rotational kinetic energy is dependent by the moment of inertia and angular velocity.

Problem solving :

 

The door rotates on its axis with a moment of inertia of 0.15 Nm and angular velocity of 10 rad / s. How Ek rotation ?

Known : I    =   0,15 Nm

             ω  = 10 rad/s

Ek = ½ I ω

     = ½ . 0,15 Nm . 10 rad/s

     = 0,75 Joule

so we can assume that if the moment of inertia of a rotating door of 0.15 Nm and angular velocity 10 rad / s the kinetic energy of rotation is 0.75 joule.

 

2.      Frictional force

Friction is the force directed against the direction of motion of objects or inclination objects will motion. Frictional forces appear when two objects come into contact. Large friction force depends on the rough and smooth surfaces friction against each other. Rough surfaces will cause friction force is relatively larger than a smoother surface, the friction force is dependent object weight but not object surface area is dependent.

static friction force

           Static friction is friction between two solid objects that are not moving relative to each other. As an example, static friction can prevent object sliding down the incline. The coefficient of static friction is generally denoted by μs, and generally larger than the coefficient of kinetic friction.
Static friction resulting from a force that is applied just before the object is moving. The maximum frictional force between two surfaces before the movement is the result of the static friction coefficient multiplied by the normal force Fn f = μs. When no movement occurs, frictional forces can have a value of zero to the maximum friction. Each style is smaller than the maximum friction force trying to move one of the objects will be countered by the force of friction is equal to the force but opposite direction. Any force larger than the maximum friction will cause the movement occurs. Once movement occurs, static friction force can no longer be used to describe the kinetics of object, making use of kinetic friction.

Kinetic friction force

          Kinetic friction (or dynamic) occurs when two objects move relative to each other and friction each other. The coefficient of kinetic friction is generally denoted by μk and generally always smaller than the static friction for the same materials

Types of friction

There are two kinds of friction between two solid objects together moving forwards, the static friction and kinetic friction, which differentiated between the touch points between the two surfaces that remain or are changing (shifting). For objects that can be rolled, there is also another type of friction is called rolling friction (rolling friction). For a rotating object perpendicular to the surface or air-spin, there is also friction spin (spin friction). Frictional forces between the solid and the fluid is called the Carioles force-Stokes or viscous force (viscous force).

Frictional force advantage and disadvantage

Examples of advantage friction force:
a. Footwear shoes and sandals made ​​of rubber and the like, and form is such that if used will resist use in   order not to slip.
b. Car tires, bicycle tires and motorcycle tires are made of rubber and form in design so that zoom in friction between the tire with road was also made rough.

Examples of disadvantage friction force:
a. Gir wheel and chain on the bike and a motorcycle or other parts that are friction can wear and damage. work reduce this friction can provide oil as a lubricant
b. In the car, motorcycle, or machines in the factory is always friction between the parts of the machine that quickly wear out or damaged. work reduce the this friction can provide oil as a lubricant.

purpose:
a. Determine the coefficient of static friction and kinetic coefficient of friction of the two surfaces
b. Determine the speed and acceleration of the motion on an inclined plane

-          The coefficient of static friction coefficient of friction between the two surfaces collide silent.

-          The coefficient of kinetic friction: the friction coefficient of the objects that collide in which objects move relative to one another.

The coefficient of friction arises because of the combination of two surface therefore the friction force vector is always painting on the surface of the meet.

Tools and materials:                                         
1. surfboard
2. block of wood
3. ruler measuring
4. stopwatch

Procedures:
*  Determine the coefficient of static friction
1. Put a block of wood on surfboard
2. Slowly lift surfboard until block reaches a position where the block will move right. Stop lifting and hold the surfboard in position.
3. Measure the price of x and h. Enter the data field
4. Repeat steps 1,2 and 3 with prices of different x
5. Calculate the coefficient of static friction

* Determine the coefficient of kinetic friction
1. Put a block of wood on surfboard
2. Slowly raise and stop the surfboard from sliding block current at the time and stop the stopwatch turn right when block reaches the end of the surfboard. Record the time in the field of data
3. Measure the distance x, h, and s in that position and record the data field
4. Repeat steps 1,2 and 3 with different price x
5. Calculate the coefficient of kinetic friction it

3.     Calculating Electrical of resistance circuit

In generally, circuits resistance classified into circuit of series resistance, parallel resistance, or a combination of both. To create a series or parallel resistance circuit a minimum of two resistance. Meanwhile, to make a circuit series-parallel combination of resistance required at least three resistance. The types of circuit resistance has its own advantages and disadvantages of each.

Series circuit

        The circuit is one of the series circuit are arranged on equal footing (series).  Two or more resistance are arranged in a sequence called the series resistance. Resistance in series to form an electrical circuit is not branched. current flowing at any point of the same magnitude. The purpose circuit series resistance to increase the value of electrical resistance and dividing the potential difference of the voltage source. The circuit resistance can be replaced with a series of resistance called substitute series resistance (Rs).

Parallel circuit

        Parallel The circuit is one electrical circuit arranged lined up (parallel). Two or more resistance are arranged side by side called parallel resistance. resistance are arranged parallel to form electrical circuits branched and have more than one lane of electric current. Arrangement of parallel resistance can be replaced with a resistance called substitute resistance parallel (Rp).

Series circuit - Parallel of Resistor (Mixed)

        circuit mix is a combination of resistor series circuit with resistor parallel circuit. mixed circuit is a circuit that is composed of a series circuit and parallel circuit in a single circuit for example, look at the picture.

Problem solving :

What is the total R value of a circuit mixed ((R1 + R2) / / R3) + R4 ?

Known :

R1 = 3 ohm

R2 = 3 ohm

R3 = 6 ohm

R4 = 7 ohm

Answer :

Rs   = R1 + R2

       = 3 ohm + 3 ohm

       = 6 ohm 
1/Rp    = 1/Rs + 1/R3

            =  1/6ohm  + 1/6ohm 

            =2/6 ohm         

 Rp      =  3 ohm

                       
 R total       = ((R1+R2)//R3) + R4               

                  = (Rs//R3) + R4                                             

                  = Rp + R4                                                      

                  =  3ohm + 7ohm                             

                  = 10 ohm                                                                

                                                                                                                                          

                                                                                                           

4. Sound as a wave

         The waves are part of the energy vibrations that propagate. Sound waves can not propagate in a vacuum because there is no in the room air particles in the air.

            Wave by the medium can be divided into 2 types:Mechanical waves in the wave propagation need a medium. Examples of mechanical waves are sound waves.
- Electromagnetic waves are waves that do not need the propagation medium. Examples of electromagnetic waves are light wave 

Wave direction to knock divided into 2 types:
- Transverse waves are waves that knock the direction perpendicular to the direction of vibration. For example, light waves.
- Longitudinal waves are waves that knock the direction parallel to the direction of vibration. Longitudinal wave consists of density and strain

The waves can be used in everyday life such as artificial satellites, solar cells, sonar, and oil and gas exploration.

sound is a mechanical wave that is longitudinal. According frequency sound waves are divided into 3 infrasonic, and ultrasonic audiosonic. The third sound is the result of the vibration of an object. Vibration sound sources surrounding air vibrate and propagate all directions as a longitudinal wave. Sound waves are collected by the outer ear and the eardrum vibrate further.
Wave  type sound is just sound audio that can be captured by the human ear. Sound waves propagate in the form of density and strain so that the sound can travel through solids, liquids, and gases. Sound waves are very easy to experience diffraction. That is why we can hear the sound of a car engine before the bend in the road even though we have not seen the car because it was blocked by tall buildings alongside a bend.