Newton’s laws feel abstract until students push something and watch what happens. The free PhET simulation Forces and Motion: Basics lets students run a tug-of-war, push crates with and without friction and measure acceleration. This lab turns it into a structured lesson for grades 6–10.
In this guide8 sections
Lab at a glance
- Grade level: 6–10
- Time: 50–60 minutes (or two shorter sessions)
- Objectives: calculate net force; predict motion from balanced and unbalanced forces; describe how friction and mass affect motion.
Know the simulation
- Net Force: a tug-of-war cart with pullers of different sizes on each side.
- Motion: apply a force to objects and watch speed change.
- Friction: adjust friction and see how it opposes motion.
- Acceleration: measure acceleration for different forces and masses.
Step-by-step lesson plan
- Hook (5 min). “If two teams pull with the same force, what happens?”
- Net Force (12 min). Students test balanced and unbalanced combinations and calculate net force each time.
- Motion (10 min). Apply a constant force and observe speed. What happens when the force stops?
- Friction (10 min). Repeat with friction on. Compare how far the object slides.
- Acceleration (10 min). Change force and mass; record acceleration in a table.
- Exit ticket (5 min). Explain one result using Newton’s laws.
Worksheet questions
- Left team pulls with 100 N, right team with 150 N. What is the net force and which way does the cart move?
- What happens to the cart when forces are balanced?
- In Motion, what happens to speed while a constant force is applied with no friction?
- What happens when you stop pushing with friction on? With friction off?
- How does doubling the mass affect acceleration for the same force?
- Write the relationship between force, mass and acceleration.
Answer guide
| Question | Expected answer |
|---|---|
| 1 | 50 N to the right; the cart accelerates to the right. |
| 2 | No change in motion; if at rest, it stays at rest. |
| 3 | Speed keeps increasing. |
| 4 | With friction, it slows and stops; without friction, it keeps moving at constant speed. |
| 5 | Acceleration is halved. |
| 6 | F = m × a (Newton’s second law). |
Common misconceptions
- “A force is needed to keep something moving.” Without friction, objects keep moving at constant speed.
- “Balanced forces mean no motion.” Balanced forces mean no change in motion.
- “Heavier objects always fall or slide slower.” Discuss the role of friction and net force.
Extensions
- Graph acceleration vs. force from class data.
- Connect to projectile motion with our PhET projectile motion lab.
- Explore energy in our Energy Skate Park lab.
Frequently asked questions
What is net force in Forces and Motion: Basics?
The total force after combining all pushes and pulls, including their directions. Unequal teams produce a net force toward the stronger side.
What grade is Forces and Motion: Basics for?
It suits grades 6–10, from introductory force concepts to Newton’s second law.
Is the simulation free?
Yes, PhET simulations are free to use online.
Forces and Motion: Basics turns Newton’s laws into experiments students can run themselves. Browse more in our science lab guides.
