22. IP A school yard teeter-totter with a total length of 5.2 m and a mass of 36 kg is pivoted at its center. A 18 kg child sits on one
end of the teeter-totter. (a) Where should a parent push verti
cally downward with a force of 210 N in order to hold the
teeter-totter level? (b) Where should the parent push with a
force of 310 N? (c) How would your answers to parts(a) and (b)
change if the mass of the teeter-totter were doubled? Explain.

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 objects are acted upon by only one force. gravity. mass times the acceleration of gravity (-9.81meters/second squared).