What are Forces?

Back to Physics Grade 9/10

This is a simple physics tutorial aimed at grade 9 to 10 level students (e.g. GCSE students).


What are forces?

They're around in every day life, but they're something that we take for granted: forces. By definition a force is something that occurs when two entities interact with each other. As a result of this interaction there can be a change in movement, or a change in shape.

The world around us is complicated, and there are times when both a change in shape and movement occur as a result. A good example of this in everyday life is the bouncing ball. As it impacts with the ground, it exerts a force on the ground, and the ground exerts forces on it. This force changes the shape of the ball at the point of impact, but it is also what propels the ball in the bounce.

NB: You'll notice that the video slows down around the time that the ball hits the ground - this is to show you the change in shape associated with the impact. In reality, the ball would be travelling at its fastest speed at this point. We'll learn why that's the case in more detail in future tutorials.


Pushing and Pulling Forces

Forces can be described as being either pushing or pulling, and if you take a moment you'll be able to think of many examples in everyday life. When you push something, you are exerting a pushing force; for example when you push your chair in at the table after dinner. This causes the chair to move.

You can also exert pushing forces that cause changes in shape. For example when you put you head down on your pillow at night, you are exerting a pushing force on your pillow that causes it to change shape. Similarly, when you squeeze play-doh between your fingers, the pushing force creates a change in shape in the play-doh.

NB: Mouse over the image above to see how a pushing force down changes the shape of the green play-doh.


Forces can be exerted/felt from a distance

Entities don't always need to be touching one another to exert a force. A magnet is a good example of something that exerts a force without contact; it exerts a pulling force. When a paper clip is brought close enough to it, it is drawn towards the magnet by this pulling force. Gravity is another good example; the pull of gravity keeps the earth orbiting the sun.


Notes

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