Sectieoverzicht

  • You probably have heard the word 'force' quite often. But have you ever stopped to think about what a force really is? What do you understand by the word 'force'?

    Have a look at the clip below. Are there forces involved? What kinds of forces are they and can you name any of them? How would you describe what you see happening?

      

    This is what you might have said you see happening.

    I see a ball lying still on the ground. It is at rest. When the boy kicks the ball, it lifts off the ground and moves through the air, towards the net. When it hits the net, the ball’s motion changes. The shape of the net also changes. The ball then falls to the ground, rolls along for a while, and then comes to rest again. The net wobbles in the frame for some time, until it, too, stops moving.


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      Activity 1: What is a force?

      Time required:
      • 5 minutes

      What you need:
      • A ball

      What to do:
      1. Do this activity with a friend or partner. Stand about 5 m apart.
      2. Place a ball on the ground next to you. Does the ball move on its own? Are there any forces being applied to the ball? Think about why the ball does not float away?
      3. How would you move the ball to your partner without carrying it to them?
      4. In whatever way you like, move the ball to your partner. How did you do it? Was a force applied to the ball? What applied the force? What other forces acted on the ball?

      What did you find:

      When you placed the ball on the ground, it did not move by itself. But this does not mean that there were no forces acting on the ball. There were just no forces acting to move the ball away from you.

      While the ball did not roll away by itself, it also did not float away. This is because the force of gravity kept it on the ground. However, the ball also did not sink into the ground because the ground pushed up on the ball as well. The force of gravity pulled the ball down and the ground pushed the ball up. These forces were the same size but acted in different directions. We say they were balanced.

      Balanced forces

      To move the ball to your partner, you have to kick it, roll it or throw it to them. When you do this, you apply a force to the ball. If you kicked the ball, your foot applied this force. If you rolled or threw the ball, you hand applied this force.

      Whether you kicked, rolled or threw the ball, you might have noticed that as you applied the force to the ball, you 'felt' it. This was the ball applying an equal force to your foot or hand that acted in the opposite direction.

      Kicking ball

      As the ball moved to your partner, you might have noticed that it slowed down as it moved along. This was because the force of friction (either the ground ro the air) was acting on the ball in the opposite direction to its motion.

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      A simple definition of force

      The easiest way to think about force is that it is a push or a pull on an object because of an interaction with another object. When you kick a ball, your foot (an object) interacts with another object to push it.

      1. All forces can be categorised as a push or a pull.
      2. All forces are applied to an object die to its interaction with another object.

      We can define a force as a push or pull upon an object resulting from that object's interaction with another object.

      Which of the images below show a pushing force? Which one shows a pulling force? In each case, what objects are interacting?

      Push

      Pull

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      Activity 2: Force actions

      Time required:
      • 15 minutes

      What you need:
      • A pen/pencil
      • A piece of paper

      What to do:
      1. Do this activity with a friend or partner. Together, list as many examples of actions from your everyday life as as you can think that involve forces of e.g., kicking a ball, riding a bicycle, and walking. You should be able to list at least 15.
      2. Now categorise each of these as a push or a pull. You might be able to categorise some as both. For example, when moving something like a book, you could push to pull it.
      3. For each action, identify which objects are interacting.

      What did you find:

      An example you might have come up with was picking up a school bag. In this case, the force would be a pull and the objects interacting would be your arm and hand and your school bag.

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      Watch: What is force?

      Watch this video for an excellent summary of what forces are. As you watch, think about all the other forces you experience in your everyday life.

    • Lesson 1 Quiz Test
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