First dynamics question

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Anonymous

First dynamics question 2016-01-05 14:36:02 Post No. 7763588

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First dynamics question 2016-01-05 14:36:02 Post No. 7763588

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Sorry if this is a dumb question

Just started on MIT's OCW dynamics course, very first problem I've gotten wrong but don't see what I did wrong

pic related

Can anyone explain what I did wrong to get this answer?

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>>7763588

The fuck is this?

Dynamics is supposed to be done with diffy Qs, not these high-school tier formulas.

Also step 4 you squared v2 but already took the root on the RHS. It should just be v2 without raising the power.

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>>7763601

>Dynamics is supposed to be done with diffy Qs, not these high-school tier formulas.

First dynamics question, comrade

>Also step 4 you squared v2 but already took the root on the RHS. It should just be v2 without raising the power.

Thanks, I knew it would probably be something stupid asf

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>>7763606

What the fuck... why did you use energy? This is literally high school Calculus. Fuck, not even. It's literally Algebra II; you don't need to know any physics to be able to understand/solve this problem.

I'll type out the work in just a second.

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>>7763588

>>7763606

[math]y(t)=80t\sin(60)-\frac{1}{2}32.174t^2\\

x(t)=80t\cos(60)\\~\\

y(t)=40t\sqrt{3}-16.087t^2\\

x(t)=40t\\~\\

h=40t\sqrt{3}-16.087t^2\\

55+h=40t\\~\\

h\approx63.8397 ft \approx63.84 ft\\

t\approx2.97099 s \approx2.971s[/math]

And that's all. Nothing but a simple system of equations. All thanks to basic Algebra and a bit of Calculus/derivative knowledge.

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>>7765083

Let me try reformatting that...

[eqn]

y(t)=80t\sin(60)-\frac{1}{2}32.174t^2\\

x(t)=80t\cos(60)\\

y(t)=40t\sqrt{3}-16.087t^2\\

x(t)=40t\\

h=40t\sqrt{3}-16.087t^2\\

55+h=40t\\

h\approx63.8397 ft \approx63.84 ft\\

t\approx2.97099 s \approx2.971s

[/eqn]

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>>7765083

>>7765084

>>7763588

>>7763606

Fuck it, I'm just going to upload it as a picture. You're welcome.

>pic related

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>>7763601

m8, linear Diffy Q's can be reduced down to simple algebra.

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>>7763588

>> 2016

>>>using the flat earth approximation and treating the atmosphere as a vacuum to calculate the trajectory of a projectile

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>>7765084

the latex here is brain damaged

it'll work if you put a lot of white space around the commands

[eqn]

y(t)=80t \sin(60)-\frac{1}{2} 32.174 t^2 \\

x(t)=80t \cos(60) \\

y(t)=40t \sqrt{3} - 16.087 t^2 \\

x(t)=40t \\

h=40t \sqrt{3}-16.087t^2 \\

55+h=40t \\

h \approx 63.8397 ft \approx 63.84 ft \\

t \approx 2.97099 s \approx 2.971s

[/eqn]

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>>7763601

>Dynamics is supposed to be done with diffy Qs, not these high-school tier formulas

You're that cunt who likes to lord his slightly more advanced classes over the younger students to give the impression that he is smarter than they are because they're still in first year mechanics while he knows all about the much deeper physics of second year mechanics. I remember students like you.

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>>7765177

bump

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>>7765166

No you fucking mongoloid. "Dynamics" by definition refers to time dependents DEs. That is why using an energy balance defeats the entire purpose of the introductory exercise.

No one thinks calc is advanced, just shut the fuck up with your stupid assumptions.

Stop implying you've graduated high-school either, you would know what dynamics was if you did.

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