This paper deals with application of interactive lecture demonstrations (IALD) during lectures of general physics as a way for helping students to better understand functional dependences of physics phenomenon. IALD can be described as an active engagement learning environment in a lecture setting, where computer, sensors, interface and software of PASCO are used together with demonstration equipment. Demonstration results are projected on big screen using computer projector. Assumption – observation – explanation cycle is used during interactive lesson demonstration. During this study IALD was implemented into general physics (mechanics) course. Interactive demonstrations were given for students of Siauliai University faculty of Natural Science studying Ecology and environmental studies. Lectures were given in 2009 spring semester. The same course of kinematics and dynamics were lectured traditionally for students studying Applied biology. Multiple-choice test was used to determine impact of IALD to understanding phenomena of mechanics. It was state, that in those lectures, where IALD was used, achievements of students were better than those of students learning in traditional method. Using IALD students are motivated to be not passive observers, but active participants of education process. Students, who were studying in IALD group, positively valuated employment of interactive demonstrations in learning of physics.