Chapter 1 of 8

All 8 chapters
  1. 1Forces are pushes and pulls, readunderstood
  2. 2Measuring forces, readunderstood
  3. 3Friction, readunderstood
  4. 4More friction or less, readunderstood
  5. 5Gravity and falling, readunderstood
  6. 6Air and water resistance, readunderstood
  7. 7Floating and sinking, readunderstood
  8. 8Shape and floating, readunderstood

S2.5.1 Chapter 1

Forces are pushes and pulls

What makes a thing start to move, or stop?

Your guess

Pick one before you read on. It is fine to be wrong.

Your guess

  • You picked A. Read on. At the end, the chapter comes back to your guess.

  • You picked B. Read on. At the end, the chapter comes back to your guess.

  • You picked C. Read on. At the end, the chapter comes back to your guess.

  • You picked D. Read on. At the end, the chapter comes back to your guess.

By the end you can

  • Draw arrows to show the direction of a push or a pull
  • Explain that forces can change speed, direction and shape

You open a door. You kick a ball. You squeeze a sponge. Each time you use a force.

A force is a push or a pull. A push moves a thing away from you. A pull brings a thing towards you.

Draw it first

Draw a push and a pull

  1. Three rows. Each row has a box with one arrow. In the first row the arrow points right, labelled push. In the second row the arrow points left, labelled pull. In the third row a longer arrow points right, labelled big push.push

    1 Draw a box. Draw an arrow pointing right. Write push.

  2. Three rows. Each row has a box with one arrow. In the first row the arrow points right, labelled push. In the second row the arrow points left, labelled pull. In the third row a longer arrow points right, labelled big push.pushpull

    2 Draw a second box. Draw an arrow pointing left. Write pull.

  3. Three rows. Each row has a box with one arrow. In the first row the arrow points right, labelled push. In the second row the arrow points left, labelled pull. In the third row a longer arrow points right, labelled big push.pushpullbig push

    3 Draw a third box. Draw a longer arrow pointing right. Write big push.

An arrow shows a force. It points the way the force acts. A longer arrow means a bigger force.

A force needs nothing alive. Wind pushes a leaf. A magnet pulls a nail. The Earth pulls a fruit down from a tree.

A force can start a thing moving, or stop it. It can speed it up or slow it down. It can turn it. It can also change its shape.

A table with two columns. The head row says Force and What changes. Row one: kick a ball, its speed. Row two: push it aside, its direction. Row three: squeeze clay, its shape.ForceWhat changeskick a ballits speedpush it asideits directionsqueeze clayits shape
A force can change speed, direction or shape.
Two pictures of a lump of clay between two pushes that point at each other. In the left picture the clay is wide, labelled clay. In the right picture the same clay is narrower and taller, labelled squeezed clay. Each picture has two arrows, both labelled push.pushpushclaypushpushsqueezed clay
Two pushes that meet change the shape of clay.

A book lies still on a table. Are there forces on it? Yes, there are two.

See it three ways

As a picture

A box stands for a book that lies still on a table. Two arrows of the same length leave the box. One points up, labelled table pushes. One points down, labelled Earth pulls.table pushesEarth pulls

In words

The Earth pulls the book down. The table pushes it up. The two forces are the same size. We say they are balanced, so the book stays still.

Try it

Push, pull and squeeze

You need: a bottle top or a small stone, a table or a smooth floor, a lump of clay, soft mud or a sponge.

Be safe: Wash your hands after you touch clay or mud.

  1. Put the bottle top on the table. Flick it with a finger. What does it do?
  2. Flick it again, from the side, while it moves. What does it do now?
  3. Put your hand in its way. What does it do?
  4. Squeeze the clay in your hand. What does it do?

What you will see: Your flick started the bottle top moving. A flick from the side turned it. Your hand stopped it. Your squeeze changed the shape of the clay. Each time you used a force.

If you cannot try it, this is what happens.
A table with two columns. The head row says You did and It did. Row one: flick it, it moved. Row two: flick the side, it turned. Row three: block it, it stopped. Row four: squeeze clay, new shape.You didIt didflick itit movedflick the sideit turnedblock itit stoppedsqueeze claynew shape

A wrong idea many people have

A thing that lies still has no forces on it.

Why it feels right: Nothing moves, so it looks as if nothing pushes or pulls.

The test that breaks it: Hold a book on your flat hand. Feel your hand push up. Now pull your hand away. The book falls. The Earth was pulling it down all the time.

What is true: A still thing can have forces on it. They are balanced, so nothing changes.

Key words

force
a push or a pull.
push
a force that moves a thing away.
pull
a force that brings a thing closer.
balanced
two forces of the same size that act in opposite ways.

Back to your guess

The answer is D: A push or a pull.

A push or a pull makes a thing start, stop or turn. A pull can move a thing as well as a push can. Wind and magnets can push and pull too. They are not alive.

Check yourself

Try each one before you look. A wrong answer tells you where to go next.

  1. Kofi kicks a ball. Which way does the arrow point?

    A ball with one arrow that points right, labelled kick.kick
    Tap your answer.

    1. Not this one. The arrow shows the way the force acts on the ball. The kick sends the ball away from the foot. Try another.

    2. Yes, that is right. An arrow points the way the force acts. The kick acts on the ball in the way it moves.

    3. Not this one. The kick sends the ball sideways, so the arrow points sideways. Try another.

    4. Not this one. Down is the way the Earth pulls. The kick is a different force, and it acts sideways. Try another.

    See the answer

    The way the ball is kicked

    An arrow points the way the force acts. The kick acts on the ball in the way it moves.

    • If you chose A: The arrow shows the way the force acts on the ball. The kick sends the ball away from the foot.
    • If you chose C: The kick sends the ball sideways, so the arrow points sideways.
    • If you chose D: Down is the way the Earth pulls. The kick is a different force, and it acts sideways.

  2. Which of these is a pull?

    Tap your answer.

    1. Yes, that is right. A pull brings a thing closer. The magnet pulls the nail towards itself.

    2. Not this one. The wind pushes the leaf away from itself. That is a push. Try another.

    3. Not this one. The hand pushes on the clay. That is a push. Try another.

    4. Not this one. The foot pushes the ball away. That is a push. Try another.

    See the answer

    A magnet draws a nail towards it

    A pull brings a thing closer. The magnet pulls the nail towards itself.

    • If you chose B: The wind pushes the leaf away from itself. That is a push.
    • If you chose C: The hand pushes on the clay. That is a push.
    • If you chose D: The foot pushes the ball away. That is a push.

  3. Amina squeezes a sponge. What does her force change?

    Tap your answer.

    1. Not this one. The sponge does not start to move. Squeezing changes how it looks. Try another.

    2. Not this one. A squeeze does not change how heavy a dry sponge is. It changes its shape. Try another.

    3. Yes, that is right. The sponge gets squashed. A force can change the shape of a thing.

    See the answer

    Its shape

    The sponge gets squashed. A force can change the shape of a thing.

    • If you chose A: The sponge does not start to move. Squeezing changes how it looks.
    • If you chose B: A squeeze does not change how heavy a dry sponge is. It changes its shape.

  4. Look at the picture. Which push is bigger?

    Two boxes, one above the other, drawn to the same scale. The first box has a short arrow pointing right, labelled push A. The second box has a longer arrow pointing right, labelled push B.push Apush B
    Tap your answer.

    1. Not this one. The arrows differ in length, so the forces differ in size. Try another.

    2. Yes, that is right. A longer arrow means a bigger force. The arrow for push B is longer.

    3. Not this one. A short arrow means a smaller force. Try another.

    See the answer

    Push B

    A longer arrow means a bigger force. The arrow for push B is longer.

    • If you chose A: The arrows differ in length, so the forces differ in size.
    • If you chose C: A short arrow means a smaller force.

  5. A book lies still on a table. The Earth pulls it down. What else acts on it?

    Tap your answer.

    1. Not this one. A still thing can have forces on it. The table pushes up and the two forces balance. Try another.

    2. Not this one. The table pushes back up on the book. That push is why the book does not fall through. Try another.

    3. Yes, that is right. The table pushes up as hard as the Earth pulls down. The forces are balanced.

    See the answer

    The table pushes it up.

    The table pushes up as hard as the Earth pulls down. The forces are balanced.

    • If you chose A: A still thing can have forces on it. The table pushes up and the two forces balance.
    • If you chose B: The table pushes back up on the book. That push is why the book does not fall through.

  6. Draw a box. Add a push to the right and a pull to the left. Make the pull longer.

    See the answer

    A box. A short arrow points right. A longer arrow points left.

    An arrow points the way the force acts. A longer arrow is a bigger force.

  7. A ball rolls straight along the ground. Ravi taps it from the side, and it turns. What did the tap change?

    Tap your answer.

    1. Not this one. A hard ball keeps its shape when it is tapped. The tap changed the way it moves. Try another.

    2. Not this one. A tap does not change how heavy the ball is. It changes the way the ball moves. Try another.

    3. Yes, that is right. The ball moved straight, and the tap made it turn. A force can change the direction of a thing.

    4. Not this one. Any push or pull can change how a thing moves. Even a tap can. Try another.

    See the answer

    Its direction

    The ball moved straight, and the tap made it turn. A force can change the direction of a thing.

    • If you chose A: A hard ball keeps its shape when it is tapped. The tap changed the way it moves.
    • If you chose B: A tap does not change how heavy the ball is. It changes the way the ball moves.
    • If you chose D: Any push or pull can change how a thing moves. Even a tap can.

Keep it

Copy this into your exercise book.

A force is a push or a pull. An arrow shows its way. A longer arrow is a bigger force. Forces can change speed, direction and shape. A still thing has balanced forces.

Draw: A box. A push arrow to the right. A longer pull arrow to the left. Labels.

Reading with a child? A short page for the adult: what this chapter teaches and three questions to ask.

No internet tomorrow? Save the whole book as one file (691 KB). It opens on any phone.