Current Events > Why does AP Physics C have to be so hard

(+) Yeah! (+)

It's like I'm taking a foreign language and I have no experience in it but they threw me into year 3

I've had Calc AB and a basic physics course at my last high school but this is like reading Sanskrit or something

A worker W is pushing a packing crate of mass m1 = 4.2kg. In front of the rate is a second crate of mass m2 = 1.4kg. Both crates slide across the floor without friction. The worker pushes on crate 1 with a force P1w = 3N. Find the accelerations of the crates and the force exerted by crate 1 on crate 2.

Am I fucking stupid? Apparently I should already know exactly how to do this because everyone else seems to get this just fine but the solution explanation immediately fucking obliterates my head
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draw the body diagram
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There has to be someone who knows physics on CE that can explain to me how to do this without throwing a shitton of arbitrary symbols and labels like F12 and F21 and free-body diagrams that are seemingly made to be as confusing as possible by the publishers of this book

Physics teacher said this book would be a great resource if you didn't get the explanations in class but I read all this and still cannot comprehend this
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BlackHorse6969 posted...

draw the body diagram

https://www.youtube.com/watch?v=a8OAcuyGyzs
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actually i think this video is clearer

https://www.youtube.com/watch?v=605qAeeS3Dg

you gotta get used to the free body diagrams. It is confusing at first, but once you figure out the basic concept it will click and you will have an "aha" moment. There is no use trying to figure out shortcuts, you need to understand how forces work in a body diagram
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If this is a VHS class then why bother? Iirc all you had to do was hand something in
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Okay so according to diagrams the equation for the first box should be F(worker) - F(box2) = ma

Or, 3 - F(box2) = 4.2a

Then the second box should be F(box1) = ma, Or, 3 = 1.6a?

So since a is shared, a=1.875 and if you plug that back into the original equation then F(box2) = -4.875

Except apparently that is incorrect, a=0.54 and I dont know what i fucked up
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watch that second video.

Your equation will be

F = m*a

F = (m1 + m2)a

rearranged to solve for a :

a = F / (m1 + m2)
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Doe posted...

Okay so according to diagrams the equation for the first box should be F(worker) - F(box2) = ma

Or, 3 - F(box2) = 4.2a

Then the second box should be F(box1) = ma, Or, 3 = 1.6a?

So since a is shared, a=1.875 and if you plug that back into the original equation then F(box2) = -4.875

Except apparently that is incorrect, a=0.54 and I dont know what i fucked up

Yeah, I took the Force(3N) and divided that by the combined masses to get an acceleration of 0.54. If I'm wrong, then I do not deserve to be a physics major and I'll drop out immediately.
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and for the force exerted on the 2nd box by the first you go back to your body diagram for box 2, which is:

N = m2*a

you have your a so just multiply it by 1.4

if the equation is confusing to you, the 2nd video i posted walks you through it. You have to understand the body diagrams first
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I remember the last nine weeks of AP Physics being pretty friggin brutal at the time.
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this textbook is fucking worthless the explanations are nonsensical
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Doe posted...

this textbook is fucking worthless the explanations are nonsensical

trust me, youtube helps a ton with this stuff. I used it all the time in college to understand concepts
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Fin_Dawg_004 posted...

Doe posted...

this textbook is fucking worthless the explanations are nonsensical

trust me, youtube helps a ton with this stuff. I used it all the time in college to understand concepts

This. Most people I know, including myself, don't bother with the textbooks. There are vastly superior ways of learning concepts on the internet.
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Okay so I watched a lecture and the guy mentioned sine = opposite and cosine = adjacent to the angle and then I figured out when angles are equal so now I can break down 2d Forces problems

So my other big obstacle right now is integral calculus. Techinally BC Calc is a pre-req to the class but they let you take it if you're taking BC Calc at the same time which I am. But my only real prior Calculus was AP Calc AB and I barely got a 3 on the AP test

So basically I have no idea what to do whenever it asks me

The force on an object of mass m is given by the equation F = -cv(t^2). If its initial velocity is v0, what is its velocity as a function of time?

Like, if you gave me something easy like f(x)= 3x^2 - 2x + 7, that's really easy to integrate because I've had AB Calc. But the explanation of the solution throws a bunch of symbols and dv/v and stuff at me and I don't know what's going on. I just have no idea how to do it and in class he sort of glided through it

Do you guys have any videos for this or anything
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bemp
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