Newton's First Law of Motion

Back to Physics Grade 9/10

Description

This is a basic physics tutorial that is targeted at GCSE (grade 9 and grade 10) standard. The associated video tutorial is on its way.







What is Newton's First law of Motion?

Newton's first law of motion is sometimes referred to Galileo’s law of inertia. It states that

Every object in a state of uniform motion tends to remain
in that state of motion unless an external force is applied to it.



What does this mean? Well let's define uniform motion first.

NB: The graphic above illustrates four different cars (blue, green, orange and purple), each moving with uniform motion.



So Newton's First Law of Motion tells us that unless an external force is applied to an object, it will remain in a state of uniform motion.

Let's look at another example. A blue block sitting on a table at rest will not go anywhere. But if you were to apply a force to the block, say for instance with your finger, then it will move.



How fast it moves depends on the size of the force. You can see this in the graphic above, whereby the finger pushing the block to the right, is doing so with a smaller force (depicted by a short arrow), than the finger pushing the block to the left (where the force is depicted by a long arrow).

Is there a relationship between force size, and the resultant effect?

Yes, there certainly is. And this brings us to Newton's second law of motion.