Principle purpose of this lecture is to present on Conceptual Physics: Newton’s Second Law of Motion. This lecture will help you understand: Force Causes Acceleration; Friction; Mass and Weight; Mass Resists Acceleration; Newton’s Second Law of Motion; Free Fall and Non-Free Fall. Acceleration depends on the net force. Acceleration is directly proportional to net force. To increase the acceleration of an object, you must increase the net force acting on it.