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Because it has been decided that the right and upwards directions in a plane are the positive directions and the left and downwards are negative. Originally, the decisions were arbitrary but conventionally agreed (in the same sort of way that North is usually shown at the top of a map).

Any displacement in a positive direction is called a positive displacement.

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Q: Why positive displacement are called positive?
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Why positive displacement pump is called positive displacement?

replacing equal quantity of liquid from cavity is called positive displacement. let understand it by an example : lets assume you fill a bath tube up to the very top - there is no room for anything else. Then step in the bath. What happens? Water flows over the sides onto the floor - right? That is positive displacement! The amount of water that comes out is exactly the volume of your foot and leg.

What is the difference between a positive and non-positive displacement pump?

Non-positive displacement has slippage inside the pump and it is a continous, variable flow. But positive displacement has no slippage inside the pump, and it is a constant flow.

Is it true that all hydraulic motor are positive displacement?

yes.only positive displacement pumps can be used in hydraulics

Why reciprocating pump is called positive displacement pump?

because they deliver a fixed quantity of the discharge irrespective of their rpm

Where we use positive displacement pumps?

A positive displacement pump causes a liquid or gas to move by trapping a fixed amount of fluid or gas and then forcing (displacing) that trapped volume into the discharge pipe. Positive displacement pumps can be further classified as either rotary-type (for example the rotary vane) or lobe pumps similar to oil pumps used in car engines.Moreover,these pumps give a non pulsating output or displacement unlike the reciprocating pumps and hence are called positive displacement pumps

If the displacement is negative 2 north and represents a positive displacement What is the direction?


What uses positive pressure to move a fluid?

positive displacement pump

A -2 displacement towards the north represents a positive displacement towards the south?

Indeed it is.

How do you start the positive displacement pump?

with actuator

What is the rate of displacement of a body called?

The rate of displacement of a body is called its velocity.

Can a position time graph tell in which directionthe displacement of an object is?

Yes. If the slope is positive, the direction of the displacement is positive (e.g. north, east, or right). If the slope is negative, the direction of the displacement is negative (e.g. south, west, or left).

What is a non positive displacement compressor?

Well it is very important factor in fluid mechanics. The term comes often in compressors and Pumps. Displacement means change of place( Fluid ), Positive displacement means at all points of operating the discharge will be the same where as the discharge in non positive displacement varies at various operating points. For clear idea on the above compare the reciprocating pump with centrifugal pump at various operating points (by throttling) discharge valve).