The Forces and Motion Basics simulation from PhET lets you push and pull a cart, a refrigerator, a crate or a person, and watch how the forces change the motion. You can add friction, compare balanced and unbalanced forces, and see why an object speeds up, slows down or keeps moving. It is free, runs in any browser on a phone, tablet or laptop, and it is a great fit for force and motion chapters in Tamil Nadu State Board (Samacheer Kalvi) Science and Physics.
What is the Forces and Motion Basics simulation?
This interactive simulation lets you create an applied force on objects such as a cart, a refrigerator, a crate or a person. You can pull from the left and the right at the same time and change the friction to see how the motion changes. Because it runs on HTML5, there is nothing to install, and it works on phones, tablets, Chromebooks and computers.
Elementary school to university
Apply forces and change friction
Phone, tablet, Chromebook, PC
English
PhET’s learning goals include identifying when forces are balanced or unbalanced, finding the net force on an object with several forces, predicting the motion of an object with zero net force, and predicting the direction of motion from a combination of forces.
Launch the Forces and Motion Basics simulation online
Tap or click inside the player and start pushing and pulling. Use the full-screen button in the player for a bigger view.
Credit: University of Colorado Boulder
How to use the Forces and Motion Basics simulation, step by step
- Predict first. Before you start, say which way the object will move and whether it will speed up.
- Pull from one side. Apply a force on one side only and watch the object move in that direction.
- Pull from both sides. Make the two forces equal and see that the object does not change its motion.
- Make the forces unequal. Make one side stronger and watch the object move toward the stronger side.
- Change the friction. Compare an object on a smooth surface and on a rough surface, and notice how friction slows it down.
Tip for students: always add up the forces with direction in mind. A force to the right and a force to the left of the same size cancel each other.
The idea behind the simulation: net force and acceleration
Fnet = Fright − Fleft ⇒ a = Fnet ÷ m
Here Fnet is the net force in newtons (N), m is the mass in kilograms (kg) and a is the acceleration in metres per second squared (m/s²). When the forces are balanced, the net force is zero and the motion does not change. When they are unbalanced, the object accelerates in the direction of the larger force.
Worked example: A 50 kg crate is pulled to the right with 300 N and to the left with 100 N. The net force is 300 − 100 = 200 N to the right, so the acceleration is 200 ÷ 50 = 4 m/s² to the right. This example ignores friction. When friction acts, subtract it from the applied force.
Force and motion key terms explained
These are the words you will meet while using the Forces and Motion Basics simulation, with simple meanings.
Force
A push or a pull. Measured in newtons (N), with a size and a direction.
Net force
The sum of all forces on an object, taking direction into account.
Balanced forces
Forces that cancel each other, so the net force is zero and the motion does not change.
Unbalanced forces
Forces that do not cancel. They change the object’s speed or direction.
Friction
A force that opposes motion between surfaces that touch. It acts in the direction opposite to the motion.
Newton’s first law
An object keeps its state of rest or steady motion unless an unbalanced force acts on it.
Inertia
The tendency of an object to resist a change in its motion. A larger mass means more inertia.
Acceleration
The rate at which velocity changes. A larger net force or a smaller mass gives a larger acceleration.
Common mistakes: Thinking an object needs a constant force to keep moving (with no friction, it keeps moving by itself), saying that no motion means no forces (balanced forces also give no change in motion), and adding forces without paying attention to direction.
Try the net force calculator (practice what you explore)
Enter the force pulling right, the force pulling left and the mass to see the net force and the acceleration. Friction is ignored. Then tap a “what if” button.
What you will observe in the simulation
| Situation | What happens |
|---|---|
| Equal forces on both sides | Net force is zero, so the motion does not change |
| Larger force on the right | The object accelerates to the right |
| No friction and no force | A moving object keeps moving at the same speed |
| Friction added | The moving object slows down |
| Heavier object, same force | The object accelerates more slowly |
Classroom activities for teachers
The Forces and Motion Basics simulation fits a single 40-minute period.
- Predict and test (10 min): students write a prediction before each trial, then check it in the simulation.
- Tug of war (10 min): students find force combinations that give zero net force and others that give motion.
- Friction comparison (10 min): compare the same push on smooth and rough surfaces and explain the difference.
- Exit ticket (10 min): students explain in two sentences why balanced forces do not change an object’s motion.
Looking for the matching chapters? Browse the Science and Physics books on TN SchoolBooks and download the Samacheer Kalvi PDFs, then use this simulation to make the force and motion lessons visual. More free science simulations and textbook PDFs are on the home page.
Quick quiz: test your understanding of forces and motion
Score: 0 / 5
Forces and Motion Basics simulation: frequently asked questions
Is the Forces and Motion Basics simulation free?
Yes. PhET simulations are free to run online in a browser. Check PhET’s licensing page for reuse terms.
Does it work on a mobile phone?
Yes. It is built with HTML5 and works on phones, tablets and Chromebooks. Use landscape mode or the player’s full-screen button for a bigger view.
What is the difference between balanced and unbalanced forces?
Balanced forces cancel, so the net force is zero and the motion does not change. Unbalanced forces do not cancel, so the object speeds up, slows down or changes direction.
What does Newton’s first law say?
An object at rest stays at rest, and an object in motion keeps moving at a steady speed in a straight line, unless an unbalanced force acts on it.
The Forces and Motion Basics simulation turns pushes and pulls into something you can adjust, test and see. Explore it, take the quiz above, and keep experimenting until predicting the motion feels easy.