Sofia sees a wagon sitting still, and she will push it so it starts moving. When the wagon starts moving, what will happen to its kinetic energy?
- It will increase. (correct answer)
- It will decrease.
- It will stay the same.
- It will become zero.
Explanation: This question tests 4th grade ability to predict how an object's kinetic energy changes when its speed changes (NGSS 4-PS3-1). Students must understand the direct relationship between speed and kinetic energy to make accurate predictions. The rule for predictions: when speed increases, kinetic energy increases; when speed decreases, kinetic energy decreases; when an object stops (speed becomes zero), kinetic energy becomes zero. This relationship is always true - speed and kinetic energy always change in the same direction. In this scenario, Sofia sees a wagon sitting still and pushes it so it starts moving. The wagon's speed will increase from zero, so we can predict its kinetic energy will increase. For example, when the wagon starts moving, it will gain kinetic energy it didn't have before. Choice A is correct because it accurately predicts that kinetic energy will increase when speed increases. This prediction follows the speed-energy rule and shows the student understands the direct relationship between these two variables. Choice D is incorrect because it predicts the kinetic energy will become zero. This is a common error where students think energy can't change. The key understanding is that kinetic energy only exists when something is moving, and more speed always means more energy. To help students make predictions: Create 'if-then' rules together ('If speed increases, then energy increases'). Practice with examples across different contexts (ball rolling, person running, car driving) to show pattern holds everywhere. Use before/after comparisons: have students predict, then observe to confirm. Emphasize that stopped objects have zero kinetic energy - energy appears when motion starts, disappears when motion stops.