How to use the shortcut for solving elastic collisions | Physics | Khan Academy

In this video, David solves an example elastic collision problem to find the final velocities using the easier/shortcut approach.
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[@kyratulamira]

this actually works, thank you so much! wish me luck for my finals next week :)

[@rokeyaakter2100]

How was your finals?

[@Hollowfires]

Thank you so much. This was extremely helpful.

[@chronic295]

Phenomenal work! This is quite valuable.

[@jaffarkeikei4323]

This' wonderful, gonna prove to Physics teacher

[@vikthorjon6592]

This is gold 👑👑👑👑❤❤❤❤

[@SuckerforMetal]

Thank you for your clear explanation, our prof didn't explain this but he still put it in our midterm

[@consoundancyaudio8720]

same

[@osama3195]

Thank you 🖤🖤

[@fentaboy4769]

Thankx

[@nicolaigetz3841]

Beautiful

[@FrankishHistory]

Thank you Khan, I'm going to pass my momentum test in my physics class

[@gridpaper2980]

THANK YOU

[@hotyogaoceanave8778]

Thank you for making that video
I totally understood it
Only request is if you could enlarge your writing
Wow thk you

[@tomertiferet2002]

Does it keep its value with springs?

[@nicholasgalliano8541]

Thanks for this - however, how would this work if the balls were heading from different angles and hitting at a specific angle at point of collision?

[@houndcake1]

Once again, Khan Academy saves my butt. Thanks guys

[@consoundancyaudio8720]

mine too

[@jhuvezbiyok8175]

What's the formula if you have to find the velocity of the second object?

[@terrellstarks7088]

Where can I find the derivation for this handy shortcut ?

[@perspective8369]

I have the same question

[@videoupload6898]

ruclips.net/video/9yXrEZy5WME/видео.html

[@videoupload6898]

@@perspective8369 ruclips.net/video/9yXrEZy5WME/видео.html

[@MegaJayLover1]

how come this only work with some problems? i tried it with a problem of mine and it gave completely wrong answers (and yes i checked my work, all calculations are correct)

[@vaishalimahindre3914]

Was it a elastic collision problem

[@PhoenixNTZ]

My teacher is saying that there is 2 sets of solutions. Can I use this method to find both sets? If so, how?

[@yumi-jx5nz]

what if the mass is unknown?

[@samuelknight618]

If the mass is unknown there is no way of calculating the final velocities if just the initial velocities are known. The final velocities would be very different between a tennis ball and a golf ball and a tennis ball and a bowling ball, even if they were travelling at the same initial velocities.

[@interview1296]

Wat

[@kristendelgado7933]

I thought tennis balls would not be considered elastic collisions because some kinetic energy is lost in the deformation of the tennis ball when it hits the golf ball??
Billard balls = elastic collisions
Tennis balls = inelastic collisions

[@dr.c.meenakshi1651]

we just consider

[@R4G3L3GiTSn1PZ]

There's a reason why in physics and similar classes you see the phrase "we will assume..." . Really messes up visualizing problems for me though lol

[@aryensujjan]

Do problems in reference to center of mass it takes 10 seconds

[@DanHartwigMusic]

Very nicely done, but please mind significant figures. The masses only provide 2 sig figs total. Very technically, we only can provide an answer up to 1 sig fig because 40 m/s and -50 m/s only provide one.
Written as 4.0*10^1 m/s and -5.0*10^1 m/s provide 2 sig figs, which would still yield -38.64 m/s and 51.36 m/s technically incorrect.
The final answers should be
Vtf = -39 m/s, and
Vgf = 51 m/s
in that case.

[@TheScienceCube]

Hey Daniel, you're absolutely correct but I guess it is more about the concept than the math :)

[@michaelmcdonald3427]

this is actually kind of useful, thank you

[@briansanchez6699]

I owe you an an apology

[@tauseefmalik551]

What is trick in that fool.
It comes from conservation of energy.