## Projectile motion is all about throwing up… (updated)

Because you’ll get sick of it!

So this is a bit of a revision post – it is apparent that we need to review the concepts behind projectile motion. So let’s start at the beginning.

Whenever an object is thrown within a gravitational field, it’s trajectory will curve in a parabolic path. This happens because the object is attracted towards the earth, so the vertical component of velocity changes. Remembering that velocity is a vector, this means that the direction and magnitude will change. Because the acceleration component due to gravity is the same direction as the vertical velocity, this means that only the magnitude of the vertical velocity will change.

Because there is no component of acceleration in the horizontal axis, the horizontal component of velocity will remain constant. When you recombine these two components, you can see how the overall direction of velocity changes. The direction will change over the entire flight until (if it remains aloft long enough, the velocity will become almost parallel with gravity).

The picture to the right shows how this changes over time. There are many excellent resources that will help you explore the concepts of projectile motion. Here are a few of the best:

1. Classroom Physics: This is probably the best one – it has a detailed explanation and animations to investigate all aspects.
2. University of Winnipeg: This has a good introduction. Use this as a secondary source.
3. PhET: has some good simulation tools, but includes air resistance. Air resistance is not part of the VCE curriculum, so only use this for exploring and investigating.
4. Physics Learning Site: This is another excellent resource. It is definitely worth trying out.

Finally, here is the first of a sequence of videos that are very good. Watch at least the first three:

Finally, here are some practice problems (1, 2, 3)for all of you; you need to keep on doing them until you can do them easily. There will be another post soon, so keep your eye out!

See you after the Holidays!

update: here is the video of the ski-jumping tires: