HSC Stuff > HSC Physics
HSC Physics Question Thread
AladinX:
--- Quote from: jakesilove on February 06, 2016, 10:23:24 am ---Hey AladinX!
Firstly, that's a seriously cool assignment! Tricky, but cool. I'm sure heaps of people on the forum will have great ideas, so hopefully everyone can contribute!
Secondly, I think we need a little more information about the project. Is the rocket launcher supposed to be accurate, or just launch a projectile further than a required distance? Is there a target? What is the required distance? How heavy is the projectile?
If you just need to launch a projectile greater than a required distance, and accuracy doesn't matter, I'd build yourself a good ol' fashion Potato Gun. Google the method, but it's cheap to make and works like a charm. You could vary the construction depending on how far you want it to go etc.
If you need accuracy, typically people build trebuchets and other similar launchers. Again, I can go more in depth when I have the answers to the above questions, but I'm thinking that building something like that would be really difficult. What I'm imagining is sort of "cheating" the question: if all that is required is launching a projectile a set distance, accurately, I would buy something like Hot Wheels tracks, set up a ramp and fling is to the point you need to get to. You can easily do the calculations, doesn't required difficult construction etc. etc.
Let me know more information! Hopefully other people on the forum have more ideas, because whilst I love theoretical Physics I am certainly not an Engineer.
Jake
--- End quote ---
Hopefully once I receive the formal assessment sheet and requirements I will be able to give you more information regarding it. Thanks for your help :)
mijomo:
Hey guys, thanks so much for having this AMA, you guys are awesome!
My first assessment task in physics this year is an open ended investigation which requires me to analyse the relationship between the surface area of an object and the rate that it falls, and then write it up as a scientific report (aim, method etc.) Just got three quick questions for you:
1. Am i right in thinking that rate of fall or the rate that an object falls at is referring to velocity and not acceleration or just the time taken to fall?
2. What are the main things I should include in my discussion?
3. When we talk about validity, reliability and accuracy, what does accuracy mean in in a scientific report context?
Thanks again for doing this AMA, LEGENDS!
jakesilove:
--- Quote from: mijomo on February 07, 2016, 03:34:13 pm ---Hey guys, thanks so much for having this AMA, you guys are awesome!
My first assessment task in physics this year is an open ended investigation which requires me to analyse the relationship between the surface area of an object and the rate that it falls, and then write it up as a scientific report (aim, method etc.) Just got three quick questions for you:
1. Am i right in thinking that rate of fall or the rate that an object falls at is referring to velocity and not acceleration or just the time taken to fall?
2. What are the main things I should include in my discussion?
3. When we talk about validity, reliability and accuracy, what does accuracy mean in in a scientific report context?
Thanks again for doing this AMA, LEGENDS!
--- End quote ---
Hey Mijomo!
Firstly, I reckon this is an epic experiment that I would have spent WAY too much time on in my HSC year. That being said, love your teacher for giving it to you!
Let's go through your questions chronologically.
Is it asking about velocity, acceleration or time?
Well, in perfect Physics world the answer would be all of the above. That's because you SHOULD be able to derive any of the other components by gathering information about one: Calculating start and end velocity will give acceleration, acceleration will give time using projectile motion equations etc.
Therefore, if your question is "What should I even be measuring?" my answer would be "That depends on the accuracy of your equipment". We will discuss what "accuracy' means further down, but my overall answer re: what the dependent and independent variable should be is as followed.
Obviously, the thing that you should "change" is the surface area of the object. The thing that you should measure will either be
a) The time the object takes to fall a set distance.
b) The velocity of the object during the fall.
c) The acceleration of the object during the fall.
You should discuss these methods, deciding which will be MOST ACCURATE. I would guess that the TIME will be the most accurate: Use your phone to film the drop, then try and slow down the footage so you can see EXACTLY how long it took to fall. This will be very accurate, and you can do subsequent calculations from there.
What should I include in my discussion
You should include things that worked, things that didn't, reason for error, explanation of results etc. etc. Basically just explain what you did, why you did it, and how successful it was. There are heaps of guides online with what you should include in a discussion: Try find whatever your textbook says!
Accuracy
Accuracy refers to how close the measured value is to the real value. For instance, the more decimal places you measure a value to be, the more accurate that measurement is. So by filming the descent, and getting the point of landing to the millisecond, is quite accurate.
Accuracy refers to the success of the instruments, so just talk about limitations to accuracy depending on the equipment you use.
I hope that this helps! Sounds like an amazing task, so if you want to keep us updated with your progress/ideas/places you need help, I would be super interested. I would also recommend googling what the relationship between surface area and velocity SHOULD be, so you know what you're looking for.
Hope this helps! Fantastic question.
Jake :)
Neutron:
Hey! I was just doing some homework and I was wondering how eddy currents cause flux leakage? So I'm doing the transmission process for electrical energy and I read somewhere that hysteresis losses can be reduced by laminating the iron core, which reduces the size of eddy currents formed but I was wondering how smaller eddy currents would help the flux leakage? Sorry if this seems dumb!
Neutron
jakesilove:
--- Quote from: Neutron on February 07, 2016, 04:07:49 pm ---Hey! I was just doing some homework and I was wondering how eddy currents cause flux leakage? So I'm doing the transmission process for electrical energy and I read somewhere that hysteresis losses can be reduced by laminating the iron core, which reduces the size of eddy currents formed but I was wondering how smaller eddy currents would help the flux leakage? Sorry if this seems dumb!
Neutron
--- End quote ---
Hey Neutron!
Not a dumb question at all! Basically, the solid magnetic core is NOT supposed to be used for eddy currents, its just to produce a Magentic field etc. So its use is as a magnet, rather than a cylinder.
However, being a conductive cylinder, and because of Lenz's law, the flowing current around the core will cause Eddy currents to be formed in the core. Remember, the purpose of the core is NOT to produce Eddy currents; that is just a result of the type of object it is.
Because of conservation of energy, any eddy currents produce must cause a reduction of energy elsewhere. Basically, this means energy is "lost" in the conversion process in the production of Eddy currents in the core, and those Eddy currents aren't useful in any way.
By laminating the core, it reduces the "size" and therefore the amount of energy removed by the Eddy currents. Essentially you put a sheet of insulator in between each sheet of metal, so the Eddy currents can't become really really big. By reducing the size of eddy currents, less energy is loss.
I hope this helps! Just remember that we don't WANT eddy currents to be produced in this process; that's just an unfortunate byproduct. By reducing the size of eddy currents, we reduce the energy lost!
Jake
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