Observer.
motion occurs when an object changes its position relative to a reference point.
motion
An object is in motion if it changes position relative to a reference point. Motion is a relative quantity and is expressed in respect to the position of another object. Example: both a car and the Earth are moving (earth is revolving around the sun) but if we express the motion of the car in respect to the Earth, we say the car is moving relative to the Earth. At the same time the earth is moving relative to the sun.
motion
Its position changes relative to a frame of reference.
motion
Motion is important because it helps us define if were moving or not. With out motion we couldn't be able to move.An object is in motion if its position changes it relative to another object.
When its position is changing relative to our position. Note: all motion is relative to something else.
If an object is in motion than its position is changing.
motion
This is called relative motion. Relative to your frame of reference, the object's motion appears unchanged, even though it's motion has actually changed.
Something that is in motion changes position, the position of the object is described relative to another object. If you chose the tree as a reference point, then the object in the pictures has been in motion because it has changed postions relative to the tree.