Why is hydraulic jack used ? Write.

it is used because

It occupies less spaceheavy loads are easily movedminimum of effort  is usedit is a bit lighter than screw jacks.

They are also less likely to jam due to rust in the screw thread.

Hydraulic jacks are often used to lift elevators in low and medium rise buildings.

A hydraulic jack uses a liquid that is forced into a cylinder by a pump plunger.

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.

Answer(a)   the matererials that are in contact, the two materials and the nature of their surfaces/// (b)/// the force pushing the two surfaces together, pushing the surfaces together causes the more of the asperities to come together and increases the surface area in contact with each other