Students learn that a force causes a change in motion, and that gravity and friction are two types of forces.
Students learn what potential energy and kinetic energy are and how they are related.
Students also learn what mechanical, chemical, and electrical energy are and how they are used. Students learn that work is done when a force moves an object. They also learn about six types of simple machines and how compound and complex machines differ. By the end of fourth grade, students will develop an understanding of the position and motion of objects. Students flick a card off of a cup and find that the quarter on the card drops into the cup.