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April 15, 2021, 07:31:29 pm

Author Topic: Physics IA2 assessment help needed  (Read 306 times)

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juicebox_441

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Physics IA2 assessment help needed
« on: March 28, 2021, 06:30:57 pm »
0
Hi everyone,
Could someone please help me out with my physics assignment? It's just the concepts that I am struggling with that's all  :)

Assignment type: Student experiment

Topic: projectile motion

Research question: "How will changes in the initial height of 9cm increments affect the distance travelled by a projectile launched from a set angle of 45 degrees to the horizontal, when velocity is kept the same? "

Aim: Answer the research question by investigating the relationship between changing heights and distance.

Collected Data: please refer to attached excel spreadsheet.

Questions I need help with:
-What are some suggested graphs to construct and analyse? We need at least 2, maximum three, graphs to refer to. I already have a graph describing the effect varying heights cause on the distance travelled (i.e. the most obvious graph) but I still need 2 more graphs to analyse.

-Since the path of the projectile is parabolic with  an angle involved, what specific equation should I refer to when calculating my "theoretical" value for distance?

-Since the initial velocity could not possibly be zero, what formula should I refer to when calculating 'u'? Considering that I have the value for time.

-As all of my measurements were read in cm, however, the measuring tape used allows for mm measurements as well, what would be my standard error? (the +/- value)

-What essential calculations would be the most obvious ones to refer to? In my case, what statistical calculations would make me seem like a complete idiot if I missed out on and did not consider calculating? I already have a few things calculated, just wanted to make sure I am on the right track.  :)

-Lastly, and this may be the stupidest question ever asked by a physics students, what is really the difference between percentage errors vs percentage uncertainty? Which one am I recommended to calculate in order to prove reliability/validity?


Such a headache, I know,  but honestly, I am aiming on acing this assignment as it is the only mark I can control besides the written research investigation, whereas I have no control over the external. Thank you. :)
« Last Edit: March 28, 2021, 06:41:37 pm by juicebox_441 »

K.Smithy

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Re: Physics IA2 assessment help needed
« Reply #1 on: March 28, 2021, 07:43:26 pm »
+4
Heya Juicebox_441!

Research question: "How will changes in the initial height of 9cm increments affect the distance travelled by a projectile launched from a set angle of 45 degrees to the horizontal, when velocity is kept the same? "

In your research question, you only need to include the variables you are investigating. So, you can remove the information regarding the launch angle and velocity (include this later on in the report however - either in the rationale or methodology).
So, your research question should be centred solely around the relationship between launch height and horizontal displacement.
You can also remove the "9cm increments" part - just talk about that later on.

-What are some suggested graphs to construct and analyse? We need at least 2, maximum three, graphs to refer to. I already have a graph describing the effect varying heights cause on the distance travelled (i.e. the most obvious graph) but I still need 2 more graphs to analyse.

In this case, it would be difficult to provide more than one graph as you are keeping the launch angle and velocity constant across all conditions.
For my assignment, the graphs I had for my raw data weren't linear so I linearised the data and then graphed that. So I had different graphs (linear and nonlinear) to display the data - that could be an option for you if there isn't a linear relationship between launch height and horizontal displacement.

-Since the path of the projectile is parabolic with  an angle involved, what specific equation should I refer to when calculating my "theoretical" value for distance?

There are no formulae on the formula sheet that relate launch height to horizontal displacement. However, I did find this formula online:



The source of this equation can be accessed here

I would discuss this with your teacher however.

-Since the initial velocity could not possibly be zero, what formula should I refer to when calculating 'u'? Considering that I have the value for time.

You can use the formulae to calculate the horizontal and vertical components of initial velocity and then use pythag to determine u.
So, a formula for the horizontal component is:
sx = uxt (if you have a value for sx
and a formula for the vertical component is:
vy = gt + uy (where vy = 0)
Once you calculate those values, you can do a vector addition (head to tail) to determine the value for u (which will be the hypotenuse of the triangle)

-As all of my measurements were read in cm, however, the measuring tape used allows for mm measurements as well, what would be my standard error? (the +/- value)

Your error for equipment like this is always half of the smallest increment. So, in your case, it would be 0.5mm, which is 0.05cm

-What essential calculations would be the most obvious ones to refer to? In my case, what statistical calculations would make me seem like a complete idiot if I missed out on and did not consider calculating? I already have a few things calculated, just wanted to make sure I am on the right track.  :)

It looks like you have thought of all of the important calculations. Just make sure you also calculate SD so you can have bars on your graphs.

-Lastly, and this may be the stupidest question ever asked by a physics students, what is really the difference between percentage errors vs percentage uncertainty? Which one am I recommended to calculate in order to prove reliability/validity?

Definitely not a stupid question! Uncertainty can be a really confusing topic to wrap your head around... There are so many different formulae and techniques... It can be very confusing. I, myself,  ~h a t e d~  error propagation with a passion in high school (and still do in uni) because I could never (and still don't) understand it ahaha.
I wouldn't worry about this too much. As long as you have an uncertainty that has been calculated correctly, you are set. 

Such a headache, I know,  but honestly, I am aiming on acing this assignment as it is the only mark I can control besides the written research investigation, whereas I have no control over the external. Thank you. :)

Try not to worry too much about the external. They are much more lenient with marking than you might expect. Have a go at the exams from last year and all of the other practice papers that QCAA has provided (which you can access here). Just try to do practice problems frequently and you'll be set :)

Good luck with the assignment, give us a shout if you have any troubles :)
Katelyn
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juicebox_441

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Re: Physics IA2 assessment help needed
« Reply #2 on: March 28, 2021, 10:30:26 pm »
+2
it would be difficult to provide more than one graph as you are keeping the launch angle and velocity constant across all conditions.
For my assignment, the graphs I had for my raw data weren't linear so I linearised the data and then graphed that. So I had different graphs (linear and nonlinear) to display the data - that could be an option for you if there isn't a linear relationship between launch height and horizontal displacement.

I was thinking of keeping my OG graph, and then make a different one where I'll focus on the max and min line of best fits and discuss those (similar to the exemplar from QCAA) and hopefully that should be enough

Thank you for helping out and making life much easier!! will definitely ask once I encounter any difficulties again  :)