MANUSIA PEMBELAJAR AKAN MENGAJAR DENGAN HATI: LINEAR MOTION

Rabu, 05 September 2012

LINEAR MOTION

In Physics, motion is a change in position of an object with respect to time.

Motion is Relative. The motion of an object depends on the reference frame that is chosen.

Based on the trajectory of motion is divided into three kinds, namely :

1. Rectilinear motion is motion-shaped trajectory straight

2. Parabolic motion is motion that parabolic trajectory

3. Circular motion is motion that circular trajectory

But the focus of the subject matter for class VIII in junior high school is a RECTILINEAR MOTION or LINEAR MOTION.

Motion is typically described in terms of distance, displacement, speed, velocity, acceleration, and time.

How the difference between distance and displacement ?

Distance

Distance is the length of the path the object travels.

Distance is a scalar quantity that does not include a direction and isn’t a vector or only has a magnitude.

Displacement

Displacement is the distance and direction of an object’s final position from its initial position.

Displacement includes both a magnitude and a direction and is an example of a vector quantity.

Because it has a direction to the direction to the right is positive and left is negative.

The following is an example to distinguish between distance and displacement:
Paijo moving from point A-B-C-D, what is the distance and displacement?

Answer :

Distance from point A-B-C-D

= AB + BC + CD

= 5 + 8 + 4 = 17 meter

Displacement from point A-B-C-D

= AB + BC + CD

= 5 + 8 + (-4) = 9 meter

Or Displacement from point A-B-C-D

= Distance final position from its initial position

= AD = 9 meter

How the difference between speed and velocity ?

Speed (v)

Speed is the distance an object travels per unit of time. In SI units, the unit of speed is meters per second (m/s). Usually the speed of an object changes as it moves from one place to another.

One way to describe the speed of an object is to measure its speed at a single instant of time. The instantaneous speed (kelajuan sesaat) of an object is the speed at a single instant of time. A car’s speedometer measures the instantaneous speed of the car.

Instantaneous speed

Figure 1.1. A car moving at a instantaneous speed on time and distance certain.

Average Speed

Average Speed Another way to describe the motion of an object is to determine the object’s average speed. The average speed describes how quickly an object moved over the entire distance it traveled. The average speed of any object is the total distance traveled divided by the total travel time:

Velocity ( v )

The velocity of an object is the speed of the object and its direction of motion. Just like displacement, velocity is a vector that has a magnitude and a direction. The magnitude of an object’s velocity is the object’s speed.