Why do particles of equal mass rebound at 90 degrees?
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5 ай бұрынWhen a moving particle collides elastically with a stationary particle of equal mass, the two particles always move away at right angles to each other. In this video we use the conservation of momentum and energy to prove this. An interesting result whose proof is surprisingly simple!
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About me: I studied Physics at the University of Cambridge, then stayed on to get a PhD in Astronomy. During my PhD, I also spent four years teaching Physics undergraduates at the university. Now, I'm working as a private tutor, teaching Physics & Maths up to A Level standard.
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@niconeuman 5 ай бұрын
Very nice video. An algebraic demonstration is that if you take the dot product of the vector equation u = v + w with itself, you get: u^2 = v^2 + w^2 + 2 v * u And that can only equal the conservation of energy equation if v * u = 0, which means they are orthogonal.
@niconeuman 5 ай бұрын
Meant v * w in the last two equations!
@DrBenYelverton 5 ай бұрын
@@niconeuman Nice, thanks for sharing!
@markusklyver6277 2 ай бұрын
This approach also gives the angle when the masses are not the same.
@asthavora9046 2 ай бұрын
thank you so much!
@mxminecraft9410 5 ай бұрын
Nice video 👍
@Inthe-way 5 ай бұрын
Thank you sir. That really was beautiful.
@DrBenYelverton 5 ай бұрын
Thank you!
@markusklyver6277 2 ай бұрын
We have u = v +w. So = ||v||² + ||w||² + 2. So 2 =0, and = 0. QED
@mxminecraft9410 5 ай бұрын
Sir do you know of any books with very difficult classical mechanics ( especially Newton laws and kinematics) questions?
@DrBenYelverton 5 ай бұрын
There are some old textbooks by S.L. Loney that I like, you'll find some very interesting problems in there. Over 100 years old, but not much has changed in classical mechanics since then so definitely worth a look!
@mxminecraft9410 5 ай бұрын
@@DrBenYelverton Great coincidence I am currently solving SL Looney Trigonometry book 😃
@DrBenYelverton 5 ай бұрын
Ah, excellent!
@mxminecraft9410 5 ай бұрын
@@DrBenYelverton sir were u referring to SL Looney's Statics and dynamics book ?
@DrBenYelverton 5 ай бұрын
That's one of them, there is also another called "An elementary treatise on the dynamics of a particle and of rigid bodies".
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