it would be a because he touches the ground when he walks
frame of reference
An origin or zero point.
Motion is relative. There must be something to compare it to.
That's right, motion cannot be measured unless you have some frame of reference within which to measure it.
:p hi
Motion is always relative, depending on the reference point. If a tree is the reference point, then the car zooming past will be moving. But, if you use the car as the reference point, then it seems as though the tree is zooming past.
It certainly is necessary. Sometimes it may be implied - for example, in practice, quite often planet Earth is used as a frame of reference. But whether it is implied, or explicitly stated, you always need a frame of reference to describe motion, or position.
It is called "reference frame"; and yes, that's the basic idea - related to what will you measure movement.
It is called "reference frame"; and yes, that's the basic idea - related to what will you measure movement.
One point of view from which to describe motion is the observer's frame of reference. This point of view defines the position and motion of an object relative to the observer. By choosing a specific frame of reference, we can describe how an object moves in relation to that reference point.
the sun
Yes. On Earth, the reference point is easy to define: it is either the ground, sky, or things. In space, it's not so easy, but we often use the Sun as a reference. Beyond the Sun, perhaps the motion of our solar system could be measured using the Milky Way galaxy as a reference.