Physics Study Topic Rejected - HELP!

[rocketboy]

Hey everyone,

 

I'm getting ready to start my IB Extended Essay in Physics, and sent a proposal to my supervisor for a study on the performance of various solid rocket engines. Unfortunately this topic was rejected because a) it involves highly explosive and flamable materials, b) apparently I need more advanced lab equipment and c) it is more like a chemistry topic.

 

So now I have a HUGE problem. I am supposed to have a topic and introduction and outline finished, and I don't even have a topic!

 

I was wondering if anyone here had any ideas for a physics topic that provides a problem which I would then come up with a hypothesis for, and then prove through experimentation. It also has to be outside of the high-school Physics curriculum, so I was thinking perhaps something on fluid mechanics or thermodynamics, since they are courses that I will need to take in aerospace engineering at university anyway.

 

Thanks SO much everyone!

 

-Jon

[mezarashi]

Fluid mechanics eh... Try studying similitude. It's pretty neat, and then you can test if your calculations match real predictions. It's more of an engineering practice than physics, but you'll need to understand the fundamentals of fluid mechanics to write up an explanation of how it works. ^^

[swansont]

If you like rockets, try water rockets. Try and calculate the water/air ratio for a given height, and try and measure it. No explosives and it's all physics.

[MetaFrizzics]

What about an experiment to independantly establish Inertial mass? You could try to set up Mach's idea of action/reaction (3rd Law) to establish inertial mass using the law of Conservation of Momentum etc. You have to choose certain ideas as axioms, and then show the consequences, and reverse the scenarios as well. You work with ratios to establish the laws and then with specific weights and measure to establish scales.

These are simple experiments but involve very subtle philosophical and scientific ideas and procedures.

 

Newton offered a poor definition of Inertial mass (the product of volume and density of a body VxD ) which is just circular. He should have found a way to define inertial mass without referring to it (in the density definition).

"The true definition of mass can only be deduced from the dynamical relations between bodies:

 

All those bodies are bodies of equal mass' date=' which, mutually acting on each other, produce in each other equal and opposite accelerations.[/i']

 

We have in this simply designated or named an actual relation of things. In general we proceed similarly. The bodies A and B receive respectively as a result of their mutual action the acceleration -a and +a, where the sense (direction) of accelerations are given by the signs. We say B has a/a' times the mass of A. If we take A as our unit, we assign to that body the mass m which imparts to A m times the acceleration that A in the reaction imparts to it. The ratio of the masses is the negative inverse ratio of the counter-accelerations. That these accelerattions always have opposite signs, that there are therefore, by our definition, only positive masses, is a point that experience teaches, and experience alone can teach. In our concept of mass no theory is involved; "quantity of matter" is wholly unnecessary in it; all it contains is the exact establishment, designation, and determination of fact."

In this key definition of inertial mass however, Mach did not specify clearly the frame of reference with respecto to which the accelerations should be measured. It is simple to see that this definition depends upon the frame of reference. Two observers in different frames accelerated relative to each other will find different mass ratios. But it is evident from his writings that Mach had in mind the frame of fixed stars as the only frame to use in his definition.

 

It should be noted that nowadays the accepted definition of inertial mass is Mach's (m1/m2 = -a2/a1 ) and not Newton's ( m = DV ). Mach's operational definition of inertial mass is one of his great contributions to Newtonian mechanics. The Machian formulation is vastly superior to Newton's. But it still needs work to make it relativistic.

 

Mach believed that in physics we should only have relational quantities, the relative distance between bodies, and relative motions. Absolute positions should not appear in theories since they don't appear in experiments.

 

Einstein changed all this by introducing frame-dependant electromagnetic forces with his interpretation of velocity in the Lorentz's force law. He also introduced a frame-dependant gravitational force. Einstein correctly pointed out that the best way to implement Mach's principle was to use only the distance between interacting bodies and their relative velocites and accerations. He himself didn't do this because he thought it was impractical. He was mistaken in this regard.

 

In fact, we can develop a purely relational physics from Mach and Weber's electromagnetic theory.