---
title: "What happens when things collide"
description: "Ask questions and predict outcomes about the changes in energy that occur when objects collide"
canonical: https://lightmysky.com/learn/science/what-happens-when-things-collide-mt_1MLi55bPnt
source: https://lightmysky.com/learn/science/what-happens-when-things-collide-mt_1MLi55bPnt.md
retrieved: 2026-10-19
---

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# What happens when things collide

Ask questions and predict outcomes about the changes in energy that occur when objects collide

Subject: Science · Area: Energy · Ages 9 to 10
Page: https://lightmysky.com/learn/science/what-happens-when-things-collide-mt_1MLi55bPnt

## Ready when they can

- Predict the outcome of a collision based on the speeds and sizes of the objects
- Explain that energy transfers from one object to another during a collision
- Describe observable changes: one object speeds up, the other slows down, sound is produced

## Lesson: What happens when things collide

You already know a fast-moving thing has more energy than a slow one. When two things bump into each other, some of that energy moves from one object into the other. That is called a collision.

*(drawing: Ball A was fast and hit Ball B, which was standing still. After the hit, Ball A slowed down and Ball B sped up.)*

**Example.** Mia rolls a fast toy car toward a car that is standing still. When they crash, the fast car slows down and the still car shoots forward. Some of the fast car's energy moved into the other car.

**Tip.** Watch closely during a collision. You will often hear a sound, since some energy turns into sound instead of staying as motion. The size and speed of each object change what happens next.

**Recap.** In a collision, energy moves from one object to another: one usually slows down while the other speeds up, and you might hear a sound.

## Practice

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

## Needs first

- [Speed and energy](https://lightmysky.com/learn/science/speed-and-energy-mt_2Um22lTBZV)

## Opens up

- [Momentum and Its Conservation](https://lightmysky.com/learn/science/momentum-and-its-conservation-mt_Nn5_DMbK1_)