---
title: "Force & Motion Vocabulary"
description: "Use technical vocabulary for force and motion — balanced forces, unbalanced forces, resultant force, acceleration, deceleration, speed, moment, lever, fulcrum, mechanical advantage — and apply these w"
canonical: https://lightmysky.com/learn/science/force-and-motion-vocabulary-mt_F3ATPTCYm6
source: https://lightmysky.com/learn/science/force-and-motion-vocabulary-mt_F3ATPTCYm6.md
retrieved: 2026-10-19
---

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# Force & Motion Vocabulary

Use technical vocabulary for force and motion — balanced forces, unbalanced forces, resultant force, acceleration, deceleration, speed, moment, lever, fulcrum, mechanical advantage — and apply these when explaining and predicting how forces affect the motion and position of objects

Subject: Science · Area: Forces & Motion · Ages 9 to 11
Page: https://lightmysky.com/learn/science/force-and-motion-vocabulary-mt_F3ATPTCYm6

## Ready when they can

- Distinguish between balanced and unbalanced forces and describe the effect of each on an object's motion
- Use 'resultant force' correctly when describing the net effect of two or more forces acting on an object
- Apply 'moment', 'lever', and 'fulcrum' correctly when describing how simple machines work

## Lesson: Force & Motion Vocabulary

A force is a push or a pull. When two or more forces act on something, they can be balanced or unbalanced. Balanced forces are equal in size and point in opposite directions, so the object's motion does not change. Unbalanced forces are not equal, so the object speeds up, slows down, or changes direction.

*(drawing: These two forces are the same size and pull opposite ways. That is balanced forces.)*

When forces are unbalanced, add them up to find the resultant force. That is the one force left over once the others cancel out. A resultant force pushing forward makes an object accelerate, or speed up. A resultant force pushing backward makes it decelerate, or slow down.

**Example.** On a seesaw, the bar is a lever and it turns around a fixed point called the fulcrum. Each person's weight creates a moment, a turning effect that depends on how heavy they are and how far they sit from the fulcrum. A heavier person sitting close to the fulcrum can balance a lighter person sitting further away, because their moments are equal.

**Tip.** Watch out: balanced does not mean no forces. It means the forces are equal and cancel out. And moment does not mean a moment in time, it means a turning force.

**Recap.** Balanced forces cancel out and keep motion the same, unbalanced forces create a resultant force that speeds up, slows down, or turns an object, and on a lever that turning effect around the fulcrum is called a moment.

## Practice

12 questions on this page, each with its working shown.

## Needs first

- [Forces Vocabulary](https://lightmysky.com/learn/science/forces-vocabulary-mt_GBY8enpzO0)

## Opens up

- [Resultant Forces](https://lightmysky.com/learn/science/resultant-forces-mt_AiWlJfvC3O)
- [Levers, Pulleys & Gears](https://lightmysky.com/learn/science/levers-pulleys-and-gears-mt_Q2k3fSwyzQ)