Mechanics (1 Viewer)

[Sy123]

Is is possible for the BOS to ask non-uniform circular motion? I can derive the equation of acceleration quite easy and I was wondering if they hold the ability to ask it since I haven't really seen any questions with non-uniform motion.

Also is 3D projectile motion in the syllabus?

I haven't learnt about half of the topic but I'm just curious as to what BOS holds the right to ask.

 

[asianese]

Pretty sure its restricted to constant angular acceleration. and no I don't think 3-D projectiles are in the syllabus.

 

[Sy123]

Pretty sure its restricted to constant angular acceleration. and no I don't think 3-D projectiles are in the syllabus.

Oh ok, do you know why 3D Projectiles aren't in the syllabus?
From what I am experimenting with, it doesn't to get more complex than simply deriving along with and
Or is there something more deeper involved?

 

[Trebla]

lol wut of course 3D projectiles aren't in the syllabus, because you don't learn about functions of more than one variable in the course and vectors in 3D space. Also, a projectile in 3D space can always be made into a projection onto a 2D plane by setting the axes appropriately.

Yes, non-uniform circular motion can be asked (it has been before) but you're not expected to know it by theory. Generally you'll be given all the information you need in the question without needing to recall any theory and be asked to apply the skills that you know to deal with the problem.

 

[Sy123]

lol wut of course 3D projectiles aren't in the syllabus, because you don't learn about functions of more than one variable in the course. Also, a projectile in 3d space can always be made into a projection onto a 2d plane by setting the axes appropriately.

Yes, non-uniform circular motion can be asked (it has been before) but you're not expected to know it by theory. Generally you'll be given all the information you need in the question without needing to recall any theory and be asked to apply the skills that you know to deal with the problem.

But why can't z in terms of t, x in terms of t and y in terms of t not be asked? We aren't dealing with multi-variable functions if we just consider the parametric forms and deal with that only?
My motivation for doing 3D is because I want to model air resistance not only parallel to the x and y axes but also to the z, so the projectile moves sideways.

 

[Trebla]

But why can't z in terms of t, x in terms of t and y in terms of t not be asked? We aren't dealing with multi-variable functions if we just consider the parametric forms and deal with that only?
My motivation for doing 3D is because I want to model air resistance not only parallel to the x and y axes but also to the z, so the projectile moves sideways.

You can't exactly do much solely with the parametric forms anyway. There isn't enough scope to ask anything useful.

If you want to model air resistance which moves the projectile sideways i.e. into or out of the page whilst keeping the point of projection fixed then this would require resolution of vectors in 3D space which I'm pretty sure is beyond the scope of the syllabus.

Besides, if there was ever an occasion you would be asked this, you would be given all the necessary information and equations to be able to solve them with existing syllabus theory. You would not be expected to recall any theory that is not in the syllabus, so there is really no point trying to learn the theory behind 3D projectiles.

 

[Sy123]

Ok then, I set myself the problem:

'A projectile is fired with velocity V at an angle theta to the x-axis. Air resistance is proportional to the velocity of the projectile. Find the distance of the point of projection to the point of landing.'

So, the only forces for the y-component would be gravity and resistance, so:



And the only force for x and z would be resistance





Integrating all equations:





But I come to the problem when doing it for z.





Now, I can't find C because when t=0 then , which is undefined....

What am I doing wrong?

 

[Carrotsticks]

I don't understand the need for Z. Your problem above is 2 dimensional, so why is there Z?

 

[Sy123]

I don't understand the need for Z. Your problem above is 2 dimensional, so why is there Z?

Ah yes, I meant that there should also be some sort of wind I guess, not resistance.
And if thats the case, say wind is 5m/s in positive z, then right?

 

[RealiseNothing]

Projectile motion is motion where gravity is the only force acting on the object though, so I can't see how 3D projectile motion is even possible. You can always rotate the x-y axis to make the problem 2D.

 

[v1]

Is is possible for the BOS to ask non-uniform circular motion?

yes kind of lol
Q5 2000 HSC and Q5 1993 HSC