Grade 3 · Science
Quarter 1 · Week 1 · TEKS + NGSS
In this Grade 3 science lesson, students will learn how balanced and unbalanced forces affect the motion of objects by planning and conducting an investigation. They will observe, measure, and record how forces acting on objects can cause movement or no movement, using hands-on activities with simple materials. This lesson integrates NGSS and TEKS standards and emphasizes scientific practices such as asking questions, using tools, collecting data, and communicating findings.
Students should understand basic concepts of motion such as moving and not moving, and be familiar with simple tools like rulers and timers. They should know what a force is in everyday terms (push or pull).
A force is a push or a pull on an object. Forces can cause objects to start moving, stop moving, or change direction. When forces acting on an object are balanced, they cancel each other out and the object does not move. When forces are unbalanced, one force is stronger or acts in a different direction, causing the object to move or change its motion.
Balanced forces occur when two or more forces acting on an object are equal in size but opposite in direction. For example, if two people push a box from opposite sides with the same strength, the box will not move because the forces balance each other. Balanced forces result in no change in motion.
Unbalanced forces happen when one force is stronger or the forces act in different directions so they do not cancel out. This causes the object to start moving, speed up, slow down, or change direction. For example, if one person pushes a box harder than another person pushes from the opposite side, the box will move in the direction of the stronger force.
Students will plan an investigation to observe the effects of balanced and unbalanced forces on motion. They will decide what object to use, how to apply forces, and what measurements to take (such as distance moved or time taken). They will think about safety and how to record their observations and data clearly.
Students will work in pairs or small groups to apply forces to objects like balls or boxes. They will try pushing from both sides equally to create balanced forces and observe no motion. Then, they will push harder from one side to create unbalanced forces and observe motion. They will use rulers to measure distance moved and timers to measure time if needed, recording all data.
After collecting data, students will organize their observations into tables or charts to show the relationship between forces and motion. They will discuss patterns such as balanced forces causing no motion and unbalanced forces causing motion. Students will develop explanations using evidence and share their findings with the class using models or drawings.
If a box is pushed equally from both sides with the same strength, what will happen to the box?
Because the forces are balanced (equal in size and opposite in direction), they cancel each other out, so the box will not move.
The box will stay still and not move because the forces are balanced.
If a ball is pushed harder from one side than the other, what will happen to the ball?
The forces are unbalanced because one side pushes harder. This causes the ball to move in the direction of the stronger force.
The ball will start moving toward the side where it is pushed harder.
Introduce the concept of forces by asking students if they have ever pushed or pulled something. Show a ball and ask what might happen if you push it from one side or both sides.
Students share their experiences with pushing or pulling objects and predict what will happen to the ball when pushed from different sides.
This activity activates prior knowledge about forces and motion and sets the stage for investigating balanced and unbalanced forces.
Guide students to plan an investigation where they will push a box or ball with balanced and unbalanced forces. Help them decide how to measure motion and record data.
Students plan the steps of their investigation, decide what tools to use, and prepare to test pushing forces on objects.
Planning helps students think critically about how to test the effects of forces on motion and what evidence to collect.
Lead a discussion to explain the difference between balanced and unbalanced forces and how they affect motion, using student observations from the investigation.
Students share what they observed and explain why objects moved or did not move based on the forces applied.
Students connect their investigation results to scientific concepts of balanced and unbalanced forces affecting motion.
Challenge students to think about other examples of balanced and unbalanced forces in everyday life, such as swings, see-saws, or pushing a wagon.
Students identify and discuss real-world examples where balanced and unbalanced forces affect motion.
Applying concepts to new situations deepens understanding and shows relevance of forces and motion in daily life.
Assess students by having them describe or write about an investigation they conducted, including how balanced and unbalanced forces affected motion, and by reviewing their data tables or charts.
Students explain their investigation process and results, using evidence to support their explanations about forces and motion.
This assessment checks students' understanding of the effects of forces on motion and their ability to use scientific practices.
Students plan the steps of their investigation, decide what tools to use, and prepare to test pushing forces on objects.
What is a force?
A force is a push or a pull on an object.
What happens when balanced forces act on an object?
The object does not move because the forces cancel each other out.
What happens when unbalanced forces act on an object?
The object moves or changes its motion because one force is stronger or in a different direction.
How can you tell if forces are balanced or unbalanced during an investigation?
If the object does not move, forces are balanced; if it moves, forces are unbalanced.
Why is it important to measure and record data during an investigation?
Measuring and recording data provides evidence to explain what happens and supports scientific conclusions.
Provide sentence starters for explanations. Use visual aids like diagrams to show forces. Allow students to work in pairs for support.
Use simple language and define key vocabulary clearly. Use gestures and demonstrations to explain forces. Provide bilingual glossaries if available.
Challenge students to explain how changing the size or direction of forces affects motion. Have students create models or drawings to represent forces and motion. Encourage students to design their own experiments with different objects.
Encourage students to observe and describe forces at home, such as opening doors, pushing toys, or using magnets, and share their observations with the class.
Students learned that forces are pushes or pulls that can affect motion. Balanced forces acting on an object result in no motion, while unbalanced forces cause the object to move or change its motion. Through planning and conducting an investigation, students observed these effects, collected data using measurement tools, and explained their findings using evidence. This understanding helps explain many everyday phenomena involving motion and forces.
Use the exact standards alignment and retrieved-source provenance stored with this enrichment.