Rabu, 26 Desember 2012


Full name : Triana Siska Dewi
Student number : RSA1C311007


1. When I still study at senior hight school I often play baseball. Of course when it hit a ball thrown by our friend feels very sick. However, the pain that we feel is related to the kinetic energy possessed by a baseball. Where the kinetic energy is the energy possessed by a moving object whose size is proportional with half the mass multiplied by the square of the velocity.
Ek = ½ m v ^ 2
So when we throw a ball whose mass is greater more than normal with great pace then when we hit the ball it will be more painful.
Try it you compare:
A. Budi throw a baseball a mass of 0.5 kg with a speed of 10m / s.
B. Andi threw baseball's mass 0.5kg with speed 20m / s.

If both balls are about Yudi, which blows more pain felt by Yudi?

Course the ball is thrown by Andi is not it?
            A. EkA = ½ 0.5 kg (10m / s) ^ 2
                        = 2.5 joules

            B. Ek
B = ½ 0.5 kg (20m / s) ^ 2
                        = 5 joules

Well, from the above events, we can conclude that the greater the kinetic energy possessed by the ball the greater the pain of what when on us.

But how about we throw a ball up that will fall on a hard surface and soft soil or muddy?

2. Kinetic frictional force
Kinetic or dynamic friction force occurs when two objects are moving relative to each other and rubbing each other. In general, obtaining the kinetic frictional force is smaller than the static friction force for the same material. Where the size of the force depends on the friction coefficient of the touch of the two objects.

• Setting up a sled length (x) 1 meter and height (h) 0.5 meter and a stopwatch
• Place a block of wood mass 1kg above sled
• Slowly raise the land up balaok sled gliding and gliding turn when the beams start and stop the stopwatch when the beam reaches the end of the sled
• Measure the length when we picked up the sled to make the beam can slide
• Measure the length of the sled after sled lifted
• Record the time (t) required for the beam to reach the end of the skateboard
• Measure the value of the coefficient of kinetic friction 
 s is length at first = 1 meter
g is gravity = 9,8 m/s^2

3. Strong electric current is the amount of charge that flows in a conductor per unit time, or equal to a strong electric current proportional electrical charge and inversely proportional to the time.
I = q / t
I = strong electric current (A)
q = electric charge (C)
t = time (s)
 Within 6 minutes a charge of 280 C flows through a conductor. What is the current flowing during those 6 minutes?
Given: t = 6 min = 360 second
q = 280 C
Asked: I?
I = q / t
= 280 C / 360s
= 0.78 A
So, current flows for 6 minutes at 280 C charge is equal to 0.78 A.

4. Sound is a wave. Sound waves are mechanical waves because they require an intermediary in sound propagation. Where the sound propagation medium can be solid, liquid or gas. Sound wave is a wave in which the propagation lungitudinal, sound waves in the form of density and strain that occurs in a medium consecutive passes.
 Some evidence that the sound is a wave:
1) Can be reflected (reflection)
The sound could be reflected when the sound of the hard surfaces.
For example, our voice will be heard more loudly in the mosque due to the reflection of sound on the mosque walls made of stone and cement.
2) Can be refracted (refiaksi)
Refiaksi  the track of wave is slue direction after passing the boundary between two different media.
For example: we'll hear a sura lightning at night sounds sound louder than thunder in the afternoon this is due to the refraction of the sound waves.
3) Can be bent (diffracted)
Diffraction is flexing event sound waves when passing through a narrow slit.
For example: Andi room and adjacent Budi scream when Andi could hear shouting Budi when recording is different and the room is in a closed state, this is because the sound can pass through a narrow slits.

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