Projectile motion (part 5)

[Kricardose]

I am very happy to see the vidoe Projectile motion (part 5) after you give this

[bebeheuy]

I Love The Video How fast was the ball that you threw upwards It Can Increase My Knowledge

[Mjhond]

Steady I Really Like This Video How fast was the ball that you threw upwards

[djumr]

U just taught me how to be a successful gambler :P

[nightreaper999]

easier way. distance = (vi^2*cos0sin0)/g

[DontMissVideos]

For some reason i learn physics when it is taught by you, not by my teacher.

[moah2012]

would kahn's class be equivalent to an honors physics class or a college level physics class?

[7595012na]

improve ur writing for GOD sake!!

[acupuncter]

@7595012na Which would you rather have, great teaching or great writing. Give me a break will ya?

[7595012na]

@acupuncter but if one cant understand wat is he writin wat will he get frm the lesson!! i literally didnt understand some words and this cud create cnfusions in a students mind!!

SIR

[BloomBlossom]

"let me factor the t out to make it confusing" LOL!

[CRISNCHIPS12398]

I just started doing Year 12 and began projectile motion just a few days ago. Whilst my teacher is awesome, it is fantastic to have another person explaining the concept.

[gengen23100]

I am literally watching each and every physics video you have made. I have my final exam on friday and I learned nothing from my professor so these videos are really saving my physics I mark because without them I will undoubtedly fail it. So thank you so muchh.

[TheHearingDeaf2006]

Other then that thanks a million because you've helped me so much. :)

[TheHearingDeaf2006]

Ok I've seen something you've done twice now.

I'm looking at the equation (delta)d = Vi*T + at(squared)/2.

When you divide at(squared)/2 is it supposed to be -5*t(squared)/2?

[omgthatscrazyx]

this game blows

[drstingrae]

I must agrre that the 'test of testosterone' statement was LOL!

[doctormurray91]

Sal Kahn gives me a boner for physics :D

[Zanark9]

woot, zero factor property.

[jetlex1]

It would be awesome if you can show examples on interpreting story problems. It's harder to identified the given and implied values from a story...it'll help tremendously since problems on assignments and exams rarely itemize the known values to have you just do the math. Thanks!

[megaelliott]

oh yes sorry didn't read the question fully, it is equal to the displacement because displacement specifies the change in position of a point in reference to a previous position, which is the same as change in distance.

[lukasgomes1428]

so the change is distance is displacement?

[megaelliott]

no the change in distance is the difference between the initial distance(the position of the ball right before you let go of the ball) and the final distance(the point at which the ball hits the ground which essentially is the ground).

so if you let the ball go at 2 meters high and it hit the ground at 0 meters high then the distance is equal to 2 meters down or -2meters up.

[erinashleyx]

"a pure test of testotesrone" - lol!

[Winsunn307]

You do a great job of explaining super hard stuff. I'm taking Physics next year and using your videos to get a head start. Thanks.

[TheStigGTR]

If you threw the ball at escape velocity (or greater), would this predict that the ball would not return?

[khanacademy]

In the absence of air, the ball would not return (otherwise the air would slow it down)

[lukasgomes1428]

really? i thought gravity would force it towards the Earth's center

[HerrGeneralVonBraun]

why do i need friends to watch me throw the ball

lol

[billu75010]

betting not allowed prick

[sdegregorio]

Sal...maybe I'm missing the point, but when you have 0m=Vit-5t^2, you go though the steps of factoring out the t to get Vi=5t and then you plug in the time to get Vi. Why do you have to do the extra step? Aren't you able to simply plug time into the original equation? (0m=Vit-5t^2)

[calvinhobbesliker2]

Yes, but he wanted so show how the initial velocity is a function of the time it takes to reach the ground.

[cbot141]

Please help:

v(i) = 5t

seems to be in units of "m/s" on left of equation , yet simply units of "s" on the right.

[guest2031]

The 5 comes from the acceleration of gravity (10ms^-2) divided by a scalar quantity (2), the units do not change when you divide by a scalar. So on the right you have 5ms^-2 x ts(seconds) and when they multiply the s from the time and the s from the acceleration cancel to form m/s (metres per second) which is the same unit as v(i)m/s on the left.

[ChillerPhil]

Yeah, I tried this with my friend. The cool thing we found out about it was that no matter what angle we trew the ball, the total time of flight was the same as if it was throw straight up..

[gushitto]

This is good stuff!

[Demonsc]

lol your hilarious! good job

[darkfighte]

lol..fun game:)