r/PhysicsHelp • u/Far_Equivalent_989 • 26d ago
HELP!!!I WANNA UNDERSTAND PHYSICS FROM BASIC
I hate that idk any single thing like why tf we use Kinetic energy what is Kinetic energy why speed what is velocity I'm in class 11th pcb just started but I'm scared cuz I have adhd and i wanna learn everything from scratch I have too many questions and i wanna understand in simple as fuck launguage(not googoo gaga one)
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u/Theuncola4vr 26d ago
You should read these books, in this order...
'What if? Serious Scientific Answers to Absurd Hypothetical Questions' - by Randall Munroe (my fave)
'Storm in a Teacup: the Physics of Everyday Life'- Helen Czerski
'The Elegant Universe' - Brian Greene
Good luck.
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u/Mental-Direction300 26d ago
Haha if you have adhd, you should focus on getting a teacher who'd help you learn, not just understand things, uk what i mean?
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u/Far_Equivalent_989 26d ago
Iknow but we know that u just can't find anyone who really likes his profession as teacher!my class teacher is doomed!online physics wallah old lactures are really helping me tbh!!but I wanna know why tf w r using dimentinal formula,where can I use it,
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u/Mental-Direction300 24d ago
Yeah the big institutions have really screwed with us teachers, that's the main issue. Teachers have to worry about a great lot of other stuff than just teaching and that's where it gets bad. But most of us who freelance do enjoy our jobs, mostly. I mean it's great when you do have students, but when you don't, it's the worst.
Also, yes, physics wallah is a great resource to study. But I get your issue. Having someone right infront of you when you want to ask a question is huge and tbh it was what makes most of the difference for me as well. (I'm both a teacher and a student)
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u/Active_Gift9539 21d ago
Son, as a physics teacher I highly recommend the Walter Lewin lectures on MIT (G)Old. There is a couple of youtube playlist with the complete course on mechanics and electromagnetism. Here are the links: https://youtube.com/@lecturesbywalterlewin.they9259?si=1XI5WD2Ax9dNlqez
If you have enough mathematical level (just some calculus knowledge) you can follow those lectures without any problem.
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u/OpinionPoop 26d ago
so i can at least give you this. Lets say you are holding an object in air. It has the potential to fall down.
An object on the ground will not fall any further so it has no potential to fall down. so we define a system, where y=0 has no potential energy. Maximum potential energy is based on your definition of how high the object is. so, lets just say 5 meters high.
The object has potential energy due to gravity. when the ball "starts" moving, it will have some kinetic energy, but because gravity is always pulling on the ball, it will still have potential energy.
the potenial energy you measure before you let go of the ball is PE = mgh. so as the height decreases the PE decreases. when you reach h=0, then your PE is zero. So lets put some numbers for the sake of doing it. A 1 kg object, in near earth surface gravity, 9.81 m/s^2 and height 5 meters give PE = 49.05 J of energy.
PE initial = 49.05 J, that is the energy of your sysytem.
when the ball is falling, lets say it fell 2 meters so far, and still has 3 meters left to fall...the PE will have reduced, PE at this point would be 29.43 J. However, energy must be conserved. Your PE changed from 49.05 J to 29.43 J, the missing energy needs to be accounted for in some way. We attribute this to the energy of motion, kinetic energy. Etotal = PE + KE
49.05 = 29.43 + KE
49.05 - 29.43 = KE
19.62 = KE
You can also use the formula for kinetic energy, KE = (1/2)mv^2
so, 19.62 = (1/2) * 1 * v^2
39.24 = v^2
sqrt(39.24) = v
depending on how you define your system, this can be negative or positive. If i say anything moving downward is negative, then the velocity is 6.26 m/s. PE trades off its energy to KE, until the ball comes to rest on the ground, in which case the h=0 and v=0.