Push, Pull and Weight
Experimenting with balls is fun! In this hands-on lesson, you and your students will make them collide and study how balls can push each-other and people too! While exploring, students will also feel how pushing a light ball is different from pushing a heavier ball. Weight is important.
This lesson fits well together with a lesson where students push balls to discover how people use pushes and pulls to change motion.
- Give examples of objects pushing each other.
- Demonstrate and explain that colliding objects push each other and as a result, change each other's movement (speeding up, slowing down or changing direction).
- Give examples of how it is harder to change the motion of a heavier object, it requires a larger push.
NGSS AlignmentThis lesson helps students prepare for these Next Generation Science Standards Performance Expectations:
- K-PS2-1. Plan and conduct an investigation to compare the effects of different strengths or different directions of pushes and pulls on the motion of an object.
Science & Engineering Practices
Planning and Carrying Out Investigations. With guidance, plan and conduct an investigation in collaboration with peers.
Disciplinary Core Ideas
PS2.A: Forces and Motion. Pushes and pulls can have different strengths and directions.
Pushing or pulling on an object can change the speed or direction of its motion and can start or stop it.
PS2.B: Types of Interactions. When objects touch or collide, they push on one another and can change motion.
PS3.C: Relationship Between Energy and Forces. A bigger push or pull makes things speed up or slow down more quickly.
Cause and Effect. Simple tests can be designed to gather evidence to support or refute student ideas about causes.
For each group:
- Two identical heavier balls, like baseballs (or basket/soccer/volleyballs)
- One light ball that is about the same size as the heavier balls, like a whiffle ball (or a beach ball)
For the entire class:
- Open floor space where students can roll the balls in pairs.
- A few toy-cars of which some or lighter than others.
Background Information for TeachersThis section contains a quick review for teachers of the science and concepts covered in this lesson.
Students know from experience how pushing or pulling on an object can affect the object's motion. Maybe they explored how their own actions influence the motion of objects in a science lesson similar to this Push and Pull lesson plan. In this lesson, they will generalize this concept by seeing how objects can push or pull on other objects, as shown in Figure 1.
Figure 1. A car crashing into an other car is an example of an object pushing another.
People can change the motion of objects by exerting a push or pull on the object. For example, you push a box to make it move, and you push harder to make it move faster. In a similar way, objects can push or pull another object. If a minivan runs into the rear of a small sports car waiting at a red light, both cars will push each other and consequently change their motion. The sports car will speed up, and the minivan will slow down. If it runs into a heavy truck, the heavy truck will hardly change its motion. That shows how the result of a push depends on the weight of the object being pushed. In this lesson, students will explore all this by rolling balls into each other. During the collision, the balls push each other just like the colliding cars push each other, and the pushes will change the motions of both balls.
The size of the push plays a role in its impact as well. This influence is studied in the introductory lesson on Push and Pull.
The term weight is used throughout this lesson to refer to how heavy an object is. In everyday language, weight and mass are often used interchangeably, but in science they have different meanings. Mass is a measure of how much "stuff," or matter, makes up an object. An object's mass does not depend on gravity, so it does not change based on your location (an object has the same mass on Earth and on the Moon). Weight is a measure of how hard gravity pulls on that mass, which changes with location (an object weighs more on Earth than it does on the moon). Technically, the impact a force (a push or a pull) has on an object's motion depends on its mass, not its weight. However, in the Next Generation Science Standards, students are not expected to differentiate between mass and weight until middle school, so it is OK to use "weight" with kindergarteners.