Students learn that speed is the measure of how far something travels in a certain period of time and that velocity is the measure of speed in a certain direction. Students learn how force is needed to overcome inertia in order to stop or start objects in motion, how friction and gravity affect how objects move, and how forces work in pairs.
Students learn that gravity is a force that makes every object attract every other object.
The attraction increases as the mass of an object increases, and decreases as distance between the objects increases. Students learn that friction between surfaces or as air resistance slows the motion of objects and can be controlled. By the end of eighth grade, students will develop an understanding of motion and forces. Students observe the motion of a pendulum. They explore ways of changing the pendulum's motion and observe the relationship between the motion of the pendulum and the force it exerts on dominoes.