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What does the name "How Forces Affect Motion" mean?
- The name has three main things in it.
| Part of the name | What it means |
|---|---|
| Motion | The way an object moves |
| Force | A push or a pull on an object |
| How they are related | What a force does to that motion |
Motion
The way an object moves.
Force
A push or a pull on an object.
How they are related
What a force does to that motion.
What is motion?
- Motion means a change in the position of an object.
- You already learnt this in Chapter 4.
- There you described motion using three things.
| Term | What it tells you |
|---|---|
| Position | Where the object is |
| Velocity | How fast the object moves, and in which direction |
| Acceleration | How fast the velocity of the object changes |
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Example:
- A ball rolls across the ground.
- Its position keeps changing, so the ball is in motion.
- If it covers 5 m every second, its velocity is 5 m/s.
What is force?
- A force is a push or a pull on an object.
-
A push moves the object away from you.
- Example: You kick a ball. Your foot pushes the ball.
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GIF Watch: a force is a push or a pull on an object
![Introduction - How Forces Affect Motion - [Teachoo] - Concepts](https://cdn.teachoo.com/6106865a-219c-4caa-9f00-ea02674115c9/animation-for-what-is-force-.-a-short-looping-gif-three-or-four-beats-drawn-in-the-flat-classroom-style-of-the-chapter.-beat-1-a-force.gif)
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A pull brings the object towards you.
- Example: You pull a drawer towards you to open it.
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GIF Watch: a force is a push or a pull on an object
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A force can also change the shape of an object.
- Example: You squeeze a lemon with your fingers and it changes shape.
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GIF Watch: a force is a push or a pull on an object
How are force and motion related?
- A force changes the motion of an object.
- So we can say — force affects motion.
- The motion can change in three ways.
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An object at rest starts moving.
- Example: A ball is lying still on the ground. You kick it and it starts moving.
-
A moving object speeds up or slows down.
- Example: A cricket ball is coming slowly. The bat hits it and the ball moves much faster.
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A moving object changes its direction.
- Example: A cricket ball is coming towards the bat. The bat hits it and the ball goes the other way.
What can a force change about the motion?
three ways the motion can change
An object at rest starts moving
Example:
A ball lying still starts moving when you kick it
A moving object speeds up or slows down
Example:
A slow cricket ball moves much faster after the bat hits it
A moving object changes its direction
Example:
The bat sends the ball back the other way
How are Chapter 4 and Chapter 6 related?
- Chapter 4 described how an object moves. It used position, velocity and acceleration.
- Chapter 4 never asked what causes that motion.
- Chapter 6 gives the missing part. The cause is a force.
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In short — Chapter 4 tells you how the object moved.
Chapter 6 tells you what made it move that way.
Chapter 4
Chapter 6
Describes how an object moves
Asks what makes it move that way
Uses position, velocity and acceleration
Uses force as the cause
Never asks what causes the motion
Gives the missing part
Topics we will study in this chapter
