Motion sensor for Gate Prototype

hi,
Me and my group are required to design a prototype for a gate that opens once motion is detected.
My question first is it possible ?
and what kind of sensor should I purchase, I only need a sensor for a prototype model?

Passive IR is good, normally used for this and intruder detection in fact.

?

Passive IR, or PIR.

Google "Arduino PIR sensor".
Leo..