# Newton's second law

Resultant force = mass x acceleration (F = ma). A bigger force gives a bigger acceleration. A bigger mass gives a smaller one.

Physics (school) · Part 02: Forces and Newton's laws · Card 4 of 8 · Last updated 2026-10-19

## Analogy

Pushing an empty trolley is easy. Pushing a full one with the same force barely moves it.

## Example

**Pushing a car**

mass = 1,000 kg
force = 3,000 N
a = F / m = 3,000 / 1,000
a = 3 m/s squared

## In practice

Car makers use it to work out how much engine force a car needs.

## Practice

### Flashcards

- **State Newton's second law as a formula.** Resultant force = mass x acceleration (F = ma).

### Interview questions

**A car of mass 800 kg has an engine force of 2,400 N and 400 N of drag. Find its acceleration.**

- Resultant force = 2,400 - 400 = 2,000 N
- Use F = ma, so a = F / m
- a = 2,000 / 800 = 2.5 m/s squared

## Questions people ask

### How do I use F = ma?

Write down the values you know, with SI units. Rearrange the formula for the one you want: a = F / m, or m = F / a. A 3,000 N resultant force on a 1,000 kg car gives an acceleration of 3 m/s squared. Always use the resultant force, not just one of the forces.

### Why does a heavier object accelerate more slowly?

Mass measures how hard an object is to speed up. With the same force, a larger mass gives a smaller acceleration, because a = F / m. A 2 kg object pushed by 10 N accelerates at 5 m/s squared. A 10 kg object with the same push only manages 1 m/s squared.

## Related concepts

- [Resultant force](https://studyvisually.com/learn/science/physics-school/physics-school-part-2/physics-school-part-2-concept-2)
- [Newton's first law](https://studyvisually.com/learn/science/physics-school/physics-school-part-2/physics-school-part-2-concept-3)
- [Newton's third law](https://studyvisually.com/learn/science/physics-school/physics-school-part-2/physics-school-part-2-concept-5)
- [Force](https://studyvisually.com/learn/science/physics-school/physics-school-part-2/physics-school-part-2-concept-1)

Web page: https://studyvisually.com/learn/science/physics-school/physics-school-part-2/physics-school-part-2-concept-4
Study this card in the app: https://studyvisually.com/app/learn?category=physics-school&card=physics-school-part-2-concept-4