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Surfaces and Friction Change Motion

Physical Science — Energy & Motion | Unit 1, Lesson 4 of 6

📚 Grade: 4th Grade⏱️ Duration: 45–60 minutes🔬 Subject: Physical Science — Energy & Motion

🧽➡️🧊

Rough and smooth surfaces change how quickly motion slows down.

📋 NGSS Standard:
4-PS3-1 — Use evidence to construct an explanation relating the speed of an object to the energy of that object.

🎯 Learning Objective

Students will compare rough and smooth surfaces and explain how friction changes motion.

💡 The Big Idea

Friction between surfaces can reduce motion, and rougher surfaces usually slow objects more quickly.

🔬 The Science

Science Snapshot

Surface texture affects friction, and friction affects how motion changes over time.

What is happening?

Friction is a force that resists motion when surfaces rub against one another. Rougher surfaces usually create more friction, which can slow moving objects more quickly.

Why it works that way

Friction changes motion because some kinetic energy is transferred to heat and sound as the surfaces interact. A smooth floor and a carpet produce different results because they oppose motion by different amounts.

Look for this in the lesson

Students should compare surfaces and notice how stopping distance or speed changes. They should connect those observations to friction rather than treating the surface difference as a mystery.

Ask while you read: How can you tell from the motion whether one surface produced more friction than another?

📦 Materials

🏠 Household Items to Gather

Toy car, marble, or slider
One smooth surface such as cardboard or table
One rough surface such as towel, felt, or carpet sample
Tape measure or ruler
Worksheet and pencil

📋 Printables

Student worksheet page from this lesson

🧪 Investigation

Step 1 — Predict the surfaces (5 min)
Ask which surface will let the object move longer and why.

Step 2 — Run the smooth-surface test (10 min)
Use the same start each time and record how far the object moves.

Step 3 — Run the rough-surface test (10 min)
Repeat on the rough surface without changing the object or release method.

Step 4 — Compare stopping behavior (10 min)
Notice which surface slowed the object sooner.

Step 5 — Explain friction (10 min)
Use the evidence to explain how surface type changed the motion.

💬 Discussion Questions

Which surface slowed the object more quickly?The rougher surface usually did.

Why should the starting push or release stay the same?That helps you tell whether the surface caused the change.

What evidence would support a friction claim?Distance traveled, stopping point, or how quickly the object slowed.

🚀 Extensions

Extension: Try a third surface and rank the surfaces from least friction to greatest friction using evidence.

👩‍🏫 Parent/Teacher Notes

Teaching move: Let students touch the surfaces and describe them, then connect those descriptions to the motion results.

Misconception to catch: Students may think the object “wanted” to stop. Bring them back to the surface interaction as the cause.

Student Worksheet

Name: ________________________ Date: ________________________

1️⃣ Compare the surfaces

Surface	How far did it go?	What does that suggest about friction?
Smooth surface
Rough surface

2️⃣ Explain which surface created more friction

🔑 PARENT ANSWER KEY — Detach before giving worksheet to students

Sample explanation

The rough surface usually slowed the object sooner, which is evidence of greater friction. The smooth surface usually let the object keep moving longer.

✅ What Success Looks Like

Student compares two surfaces fairly.
Student identifies which surface created more friction.
Student supports the claim with motion evidence.