Ashipn sends out ultrasound that returns from the seabed and is detected after 5 seconds. if the speed of ultrasound through seawater is 1600 m/s what is the distance of the seabed from the ship?

It would be 4000 meters, since it took 5 seconds and it travels at a rate of 1600 meters per second (1600 meters for every second it travels), you would multiply 1600 by 5 (for the 5 seconds) equaling 8000, which is total distance traveled (from ship to seabed and back to ship).  you would then Divide that by two to get the distance between the ship and the seabed (just ship to seabed). or you can put it in one equation and get this (1600*5)/2=D (D=distance between the ship and the seabed.

Is a  vector quantity  that refers to "the rate at which an object changes its position." imagine a person moving rapidly - one step forward and one step back - always returning to the original starting position. while this might result in a frenzy of activity, it would result in a zero velocity. because the person always returns to the original position, the motion would never result in a change in position. since velocity is defined as the rate at which the position changes, this motion results in zero velocity. if a person in motion wishes to maximize their velocity, then that person must make every effort to maximize the amount that they are displaced from their original position. every step must go into moving that person further from where he or she started. for certain, the person should never change directions and begin to return to the starting position.

The sun's gravitational pull is weaker on the planets that are closer to it, i think.