Newton's Second Law
Newton's second law states that the resultant force on an object equals its mass multiplied by its acceleration.
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Newton's second law states that the resultant force on an object equals its mass multiplied by its acceleration.
- F equals m a
- More force means more acceleration
- More mass means less acceleration
🧠 Quick quiz
Three questions. Score 2 or more to complete the topic.
What is Newton's Second Law?
Within Physics, which covers forces, energy, waves, electricity, magnetism, light and space explained through motion and experiments, this topic explains Newton's Second Law. Physics topics explain how things move, push, heat up and carry energy, so each one here pairs a definition with a live model you can change.
Check that you can explain Newton's Second Law in your own words and give one example from everyday life. If you can do that, you have understood the core idea.
Understanding Newton's Second Law explains how the physical world behaves, from sport and transport to electricity and medicine.
Newton's Second Law in detail
Newton's second law says that the resultant force on an object equals its mass times its acceleration: F = ma. The acceleration is in the same direction as the resultant force. One newton is the force that gives a 1 kg mass an acceleration of 1 m/s².
For a given force, a larger mass accelerates less, and for a given mass, a larger force accelerates it more. In more general form, force equals the rate of change of momentum. The law is used to predict motion of vehicles, rockets and lifts, and to calculate forces from measured accelerations.
How the interactive helps you understand Newton's Second Law
Watch the force arrows in the interactive. Use any sliders or buttons it offers to change the values and see how the force arrows responds.
Before you change anything, predict the result. Then change one value at a time and check whether your prediction was right. This is a quick way to build a correct mental model of Newton's Second Law.
Real-life uses and examples
- Explain everyday devices, such as brakes, lifts or chargers, using Newton's Second Law.
- Use Newton's Second Law to make sense of a practical and its results.
- Answer “explain” questions by linking Newton's Second Law to a clear cause and effect.
Common mistakes to avoid
- Forgetting that some quantities, such as force or velocity, also have a direction.
- Mixing up Newton's Second Law with a related quantity that has different units.
- Learning the definition without testing it. Use the quiz and the interactive to check that you can apply the idea.
Frequently asked questions about Newton's Second Law
What is Newton's Second Law?
Newton's second law states that the resultant force on an object equals its mass multiplied by its acceleration.
What are the most important points about Newton's Second Law?
The main points are: F equals m a; More force means more acceleration; More mass means less acceleration.
Why is Newton's Second Law useful?
Understanding Newton's Second Law explains how the physical world behaves, from sport and transport to electricity and medicine.
How can I practise Newton's Second Law?
Open the interactive at the top of this page and change the controls one at a time. Predict the result before each change, then take the three-question quiz. A score of two or more marks the topic as complete on this device.
Which topics are related to Newton's Second Law?
Related topics in Physics include Friction, Moments and Levers, Pressure.