frame of reference was inverted from what it usually is that view of things would be normal for me if i normally walk to my friends this represents a frame of reference just three route that together so that peace is at right angles to the other two now i'm going to move in this direction if either plane at the same spot on your screen but you know i'm moving that way because you see the wall moving that way behind me but how do you know that i'm not that i think bill and the wall moving workable now the wallet that the pier and you have no way of telling whether imovie or not but now you know that i'm moving the point of it is that all motions it's relative in both cases i was moving relative to the wall and the wall with moving relative to me all motion is relative but we tend to think of one thing is being fixed and the other thing has been moving we usually think of the earth inspect and walls are usually pick to beer so perhaps you were the part of the first time when it was the wallet was moving and not doctor whom a frame of reference text of the earth is the most common frame of reference in which to observe the motion of other things that is the frame of reference that you're used to the framers baton to the table the table is bolted to the floor the florida anchored in the building and the building at firmly attached to the earth of course the reason for having three rods if the position uh... any object such as this fall can be specified using these three reference line this reference line points in the direction which we called up two different directions here than it is on the other side of the air and these two reference lines specify a plane which we call horizontal or level in this film we're going to look at the motion of object in this third frame of reference and other frames of reference moving in different ways relative to the other frame well let's look at a motion this field ball can be held are by the electra mode no i'm going to open the switch and you watch the motions of the ball the ball is accelerated straight down by gravity along the line parallel to this vertical reference blood as you can see the electromagnetic mounted on the cockpit can move i'm going to do exactly the same experiment the doc resume did but this time while a cart is moving at a constant velocity is pulled along by spring which is longer on this photograph turntable and that hold that with a constant velocity when the car passes this line be lol this week that you can see i'm going to start the cart down at the end of the table so that by the time it gets to this point by can be sure it's moving with a constant velocity i want you to watch right here so that you will see the ball falling