What does the expression “75 meters per second southeast” best describe?

Every second this thing moves 75 meters in the southeast direction. So, 2 secons will be 150 meters, 4 seconds will be 300 meters, etc.

Southeast means something in the middle between the south direction and the east direction, maybe about -45 degrees. We can apply Pythagorean theorem:

L1^2+L2^2=hip^2=(75m/s)^2

If East velocity is equal to the south velocity, both legs will be equal:

2L^2=(75m/s)^2

L^2=(75m/s)^2/2

L = square root [(75m/s)^2/2] = (75m/s)/[square root (2) ] = 53m/s

So the object is moving about 53m/s to the east and 53m/s to the south.

organ system-an organ system is a group of organs that work together to perform one or more functions. each does a particular job in the body, and is made up of certain tissues.