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Balanced and Unbalanced Forces

Physical Science — Forces & Motion | Unit 1, Lesson 1 of 6

📚 Grade: 5th Grade⏱️ Duration: 45–60 minutes🔬 Subject: Physical Science — Forces & Motion
⚖️🚗
Balanced forces keep motion steady. Unbalanced forces change motion.
📋 NGSS Standard:
5-PS2-1 — Support an argument that the gravitational force exerted by Earth on objects is directed down.

🎯 Learning Objective

Students will compare balanced and unbalanced forces and explain how they affect an object’s motion.

💡 The Big Idea

An object’s motion changes when forces are unbalanced. When forces are balanced, the object stays still or keeps moving in the same way.

🔬 The Science

Science Snapshot
Balanced forcescancel outno change in motioncan stay still or keep speedUnbalanced forcesnet force remainsmotion changesspeed or direction shiftscompare
The key question is whether the forces cancel out or leave a net push or pull.

What is happening?

A balanced set of forces does not change an object’s motion, while an unbalanced set does. The object might stay still, keep moving the same way, speed up, slow down, or change direction depending on the net force.

Why it works that way

Forces are pushes or pulls, and what matters most is how they combine. If equal pushes act in opposite directions, they cancel. If one side wins, the motion changes because the forces are no longer balanced.

Look for this in the lesson

Students should focus on change in motion as the clue. Balanced does not mean “no forces at all”; it means the combined forces do not produce a motion change.

Ask while you read: How can you tell from motion whether the forces were balanced or unbalanced?

📦 Materials

🏠 Household Items to Gather

📋 Printables

🧪 Investigation

Step 1 — Compare two situations (5–10 min)
Show one object sitting still and one object moving after a push. Ask what was different.
Step 2 — Test balanced forces (10 min)
Push from both sides with equal force and notice what happens.
Step 3 — Test unbalanced forces (10 min)
Make one push stronger and record how the object’s motion changes.
Step 4 — Sort the evidence (10 min)
Students identify which examples show balanced forces and which show unbalanced forces.
Step 5 — Explain with a claim (10 min)
Students write one claim about when motion changes and support it with evidence.

💬 Discussion Questions

How can you tell whether forces were balanced or unbalanced?Look at whether the object stayed the same or changed motion.
What happened when one force was stronger?The object’s motion changed because the forces were unbalanced.
Can an object be moving even when forces are balanced?Yes — if no force changes its motion, it can keep moving steadily.

🚀 Extensions

Extension: Try the same object on carpet and on a smooth floor. Compare how the surface changes the motion.

👩‍🏫 Parent/Teacher Notes

Teaching move: Keep the focus on evidence students can observe directly.

Misconception to catch: Many students think “balanced” always means “not moving.” Balanced forces can also mean motion stays the same.

Student Worksheet

Name: ________________________     Date: ________________________

1️⃣ Sort the Situations

SituationBalanced or unbalanced?What happened?
Object stayed still
Object moved after one strong push
Two equal pushes from opposite sides
One side pushed harder

2️⃣ Make a Claim

3️⃣ Draw a force situation

🔑 PARENT ANSWER KEY — Detach before giving worksheet to students

1️⃣ Sort the Situations — Sample Answers

Object stayed still — balanced. One strong push changed motion — unbalanced. Two equal pushes — balanced. One side pushed harder — unbalanced.

2️⃣ Make a Claim — Sample Answer

“When forces are unbalanced, an object’s motion changes.”

✅ What Success Looks Like