Physics 3.5.4a - Projectile Practice Problem 1

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  • Опубліковано 7 вер 2024
  • Practice Problem on Projectile Motion.

КОМЕНТАРІ • 250

  • @Axualkilla8392
    @Axualkilla8392 7 років тому +148

    dude thank you so much I was having a mental breakdown because of physics but you made it so much more simple

    • @maribelescaros5803
      @maribelescaros5803 3 роки тому +23

      A reminder that 4 years ago you had a mental breakdown over physics. how does it feel now that it is over.

    • @dahstroyer
      @dahstroyer 3 роки тому +14

      I'm currently going thorough the mental breakdown

    • @justinc.4558
      @justinc.4558 2 роки тому +9

      @@dahstroyer mental breakdown club

    • @keronrampersad1021
      @keronrampersad1021 Рік тому +3

      Now I’m having my mental breakdown currently

    • @zone-00
      @zone-00 Рік тому +2

      @@keronrampersad1021 bro same, we have a test tmr. im sobbing i still dont know how to solve it

  • @michaelkhalil7368
    @michaelkhalil7368 Рік тому +8

    I never write comments so when I do you know I mean this so sincerely. Physics has never ever made sense to me since middle and high school. Now in college I gotta get it so I don't fail these classes. This is the first time I've felt confident and actually understood even slightly what I was doing. So thank you Derek!!

  • @cinechromefilms4045
    @cinechromefilms4045 11 місяців тому +9

    13
    years later, this is still helpful. Thank you sir

  • @MovieTrim
    @MovieTrim 9 років тому +39

    Wow the quality and organization of his calculations as well as pace and verbal description of the problem beats even KHANA. Great quality content I'm subbed

  • @superbaby0907
    @superbaby0907 13 років тому +7

    love the fact that its colourful!
    helps to clearify things a lot!

  • @abhisheksaini-lw8li
    @abhisheksaini-lw8li 11 років тому +4

    seriously, i think people like u deserve a great prize... ive physics exam tommorow and i didnt know anything... thanks very much

  • @micheleloga2099
    @micheleloga2099 11 років тому +8

    Absolutely AMAZING! I can't get my Physics teacher to explain any of this to me and my book is too confusing to help me with these kind of problems. Thank you so much for doing this video! I understand it so much more now.

    • @gggg-gu2hl
      @gggg-gu2hl Рік тому

      Been 9 years.. how did you do?

  • @derekowens
    @derekowens  11 років тому +3

    Yes, that's correct. That's because for a projectile, there is no acceleration horizontally, so the velocity is the same the entire time, and you can find it with the equation x/t.

  • @felixtira5245
    @felixtira5245 10 років тому +2

    Thank you Mr. Owen! I've been frustrated for hours LITERALLY. This is the best video out there! 10/10!

  • @itsjasminagain
    @itsjasminagain 11 років тому +9

    Thank you! I've been having so much problems understanding this and I have my first exam tomorrow.. This helped so much!

  • @princesspat5239
    @princesspat5239 3 роки тому +3

    Thank you so much Im doing my first year of biomed but i didnt learn much about physics in high school. I know theres projectile formulas but I've been trying to find videos where they use the kinematics one since that increases your understanding. Thank you so much for making these, it was very clear!

  • @derekowens
    @derekowens  14 років тому +4

    I typically use v_0 for the initial velocity. That's v with a zero in the subscript position. It basically means "velocity at time zero" or "velocity when t=0". Then I use v by itself for velocity at some later time. Using u works also, though. Good notation definitely helps, but it's not as important as the concept.

  • @derekowens
    @derekowens  11 років тому +1

    The key here is to distinguish between the vertical and the horizontal. Once the bomb is released, it is a projectile, and there is no horizontal acceleration. There is vertical acceleration, though: gravity is pulling it down.
    It also gets more complicated when you include air resistance. Air resistance introduces some horizontal and vertical forces, which depend on the speed.

  • @claymountain1300
    @claymountain1300 10 років тому +1

    this video saved my life!! got a test tomorrow morning, but I finally understand now!

    • @gggg-gu2hl
      @gggg-gu2hl Рік тому

      Been 9 years how was the test? Did you graduate yet?

  • @currentlyindisguise8322
    @currentlyindisguise8322 8 років тому

    I m indian and from half an hour I was dealing with the concept that u made me understand in few mins thanks a lot

  • @derekowens
    @derekowens  13 років тому +2

    @Ell4Sh Yes, that approach would also work. There are typically multiple ways to set up a problem, all of which should give the same final answer. I set it up with 0 a the top because all of the motion and the acceleration are downward, in this problem, and setting it up this way makes all the displacement, velocity, and acceleration numbers positive. The other approach is fine, though.

  • @derekowens
    @derekowens  12 років тому

    One of the key points of projectile motion is that the horizontal motion is independent from the vertical motion. There is no acceleration horizontally, but there is acceleration (downward) vertically.
    A bullet fired is accelerated horizontally by the gunpowder exploding behind it, but once it leaves the barrel then it is just coasting, under the influence of gravity alone (which is downward). While it is coasting, it is considered to be a projectile.

  • @joshuabrucetaylor9897
    @joshuabrucetaylor9897 11 років тому +2

    I'm brushing up on my physics for the MCAT and these videos have been great. Thanks for uploading Derek, I really appreciate it :)

    • @RamanShrikant
      @RamanShrikant 2 роки тому

      how was mcat!

    • @gggg-gu2hl
      @gggg-gu2hl Рік тому

      Been 9 years what did you do? How’s everything?

  • @derekowens
    @derekowens  11 років тому +1

    At the start of a problem, you need to choose which direction you will call positive. You can call up positive and down negative, or you can call down positive and up negative. Pick one, and just stick with it through the whole problem. If up is positive, then the acceleration due to gravity is negative. If down is the positive direction, then the acceleration due to gravity is positive.

  • @derekowens
    @derekowens  11 років тому

    I understand your reasoning. The problem is how theta is defined. In this context, theta is the angle measured relative to horizontal.
    The equations
    Vx = V cos Θ
    Vy = V sin Θ
    assume that theta is the angle measured relative to the horizontal.
    If you called theta the angle relative to vertical, you could still solve the problem, but the sine and cosine would get switched.
    Hope that helps!
    Derek Owens

  • @derekowens
    @derekowens  13 років тому +2

    @omar3211 Acceleration near the earth's surface, due to gravity, is 9.8 m/s^2 (or very close to that). That's basically a constant (if you're on earth).

  • @Applecheria
    @Applecheria 14 років тому

    I am at the verge of failing Physics class. Chemistry was a mess and I do not want to Jeopardize my GPA! Thank you so much for your help!

  • @SBchampsXLII
    @SBchampsXLII 11 років тому +6

    Thank you so much for uploading these videos. You explain things so well, and your visuals are amazing.

  • @derekowens
    @derekowens  12 років тому +1

    @MsBiebaholic Yes, that is correct. The two equations you mention are actually the same, since horizontally there is no acceleration so the 1/2 a t^2 term reduces to zero. The larger equation simply reduces to the smaller in this case. I don't know an any easy way to memorize the equations of motion, but even if it's just by brute force or practicing, memorizing them is certainly a good idea.

  • @lizrey63
    @lizrey63 12 років тому +2

    omg you are soooooo helpful!!!!!!! im so glad i found your videos! thanks for taking the time to make these. you dont understand how helpful these are. thank you!

  • @Vlb361
    @Vlb361 11 років тому +3

    Thank you so much for making these videos! They made studying for my exam so much easier. :)

  • @derekowens
    @derekowens  12 років тому

    @SohrabR93 It depends on how the problem is set up. Typically a problem can be set up with up being the positive direction (in which case gravity is -9.8), or with down being positive (in which case gravity is +9.8). It can be done either way, as long as you pick one way and stick with it consistently through the whole problem.

  • @aaravmaheshwari3733
    @aaravmaheshwari3733 2 роки тому

    This literally just saved my whole grade, thank you

  • @EmmanuelGINI-vj8qf
    @EmmanuelGINI-vj8qf Рік тому +1

    Bro your teachings are very smart and easy
    Thank you very much

  • @derekowens
    @derekowens  12 років тому

    @Star123Euro In this problem, the object is a projectile, which means its motion influenced by gravity only. And gravity pulls straight down. The force of gravity does not have any horizontal component, so the horizontal acceleration is zero as long as it is in free flight.

  • @rdbanks2823
    @rdbanks2823 7 років тому +1

    Derek Owens - Thank you so much!
    Resolving in the Y direction makes so much sense - then you can find the time it would take to drop. This idea links nicely to your last video!!

  • @FHO72
    @FHO72 11 років тому

    holy shit, i finally UNDERSTAND. Jesus christ. I am jumping with joy right now. Thank you for making sense. Thank you. Seriously.

  • @supajustin4285
    @supajustin4285 8 років тому +1

    This is very helpful for my AP class. Thanks so much

  • @derekowens
    @derekowens  12 років тому

    @804YankeeFan Yes, that's basically correct. When I throw a ball into the air, the rotation of the earth does not cause the ball to be "left behind".

  • @Denseworldproduction
    @Denseworldproduction 14 років тому +1

    thanks WOW! your 8 min tutorial rlly helped me do a problem that wasnt even the same as this, so basically you improved my understanding :)

  • @scraggsds
    @scraggsds 10 років тому +1

    Thanks for posting this. Helped me understand it easier and made my life a lot easier.

  • @Palmar3s
    @Palmar3s 13 років тому

    @juschecknin
    because gravity doesn't affect it because it's going horizontal, that is why there is no horizontal acceleration, but if it's vertical then yes, because gravity pulls down, gravity doesn't work from side to side (horizontal) therefore there is no acceleration. As far I have seen, every time acceleration is mentioned I think of gravity working on the vertical axis, pulling down, never it acts sideways, unless there is another force of acceleration. I think it goes like that :/

  • @derekowens
    @derekowens  12 років тому

    @HairtUB It depends on how the problem is set up. If it is set up consistently, then y and a will both have the same sign in that equation, and there would be no negative square root.

  • @janithaamarasinghe4954
    @janithaamarasinghe4954 3 роки тому

    These were difficult at first but after watching these videos I understood the main concepts. I became an expert in projectile motion questions. Thank you so much for doing this :)

  • @derekowens
    @derekowens  12 років тому

    @lidyaFACE There are usually two (or more) ways to set up a problem. The acc. can be either positive or negative, depending on how it is set up. For a projectile, though, the horizontal and vertical motions are always independent, and the acceleration of gravity only applies to the vertical motion. For a projectile, the horizontal acceleration will be zero.

  • @ItsChenice
    @ItsChenice 8 років тому +3

    You sir, are a life saver!

  • @stevetari3990
    @stevetari3990 10 років тому +1

    perfect explanation, i am sure i've gained something from it....

  • @merlin88888
    @merlin88888 3 роки тому

    im just gonna leave this here... cuz im not too sure if everything required here is in the vid.
    1. A ball rolls off a table that is 1.5 m high and lands on the floor, 4.0 m away from the table.
    a. How long is the ball in the air?
    b. With what horizontal velocity did the ball roll off the table?
    c. What is the vertical velocity of the ball just before it hits the floor?
    d. What is the horizontal velocity of the ball just before it hits the floor?

  • @Purpleye815
    @Purpleye815 11 років тому +1

    Thank you for posting this is helping me study for exams

  • @tinpot1978
    @tinpot1978 9 років тому

    It's easier to use the equation Vo = range x square root of gravity divided by 2 x the height... i.e. 2 time the height is 200... 9.8 divided by 200 is 0.049... square root of 0.049 is 0.22135. times that by 95 (the range) and you get the answer 21.029. No need to find the time.

  • @derekowens
    @derekowens  14 років тому

    @alkhor999 I typically use x to indicate the horizontal position and y to indicate the vertical position.

  • @1234567890585
    @1234567890585 11 років тому +1

    Your tutoring skills is very good, but there's still a thing which I would like to clarify: when will you know that acceleration due to gravity is positive or negative? In what circumstances?
    because every in every Physics class, they will use positive and negative values of acceleration due to gravity. Please help. Thanks in advance.

  • @SohrabRouzbeh
    @SohrabRouzbeh 12 років тому +1

    thanks man,grate explanation,but i don't know why in some cases other lecturers put gravity as -0.98 but it wasn't negative here!

  • @SuperMmmm33
    @SuperMmmm33 12 років тому +1

    you are amazing!, ths tutorial helped me with a problem that i've been struggling with for days! :)

  • @avgrech
    @avgrech 13 років тому

    10x a million ma 2 morro i got a test aout thease and i was sick all week no idea what to do but now i got a clue 10x m* ur da best vry good explenation btw

  • @isome9123
    @isome9123 8 років тому +1

    Great vid as always! I have a question however (hope it's not too foolish): Why do we use the same t in the horizontal equation as the one we used in the vertical one? Maybe I interpret it wrong but doing so wouldn't it mean that it takes the same amount of time to move in a horizontal and vertical way independently? And if so, how do we know it does this? Hopefully I managed to explain my misunderstading well.

  • @derekowens
    @derekowens  13 років тому

    @anoorcc Not in this case. If it were a symmetrical parabola, going up and then back down, then we could double the t to find the whole time. In this case, though, we only have half of such a parabola.

  • @lylass1232
    @lylass1232 10 років тому

    Good video. It help me to understand better in this chapter. Good job!

  • @riceisnice8643
    @riceisnice8643 Рік тому

    thanks for helping me I was on the verge of crying

  • @AdityaKumar-dm9jz
    @AdityaKumar-dm9jz 3 роки тому

    T=root 2h/g
    U will get t and then
    Sx = Uxt
    Puting the value of t in above equation u will U

  • @mattmeyer8141
    @mattmeyer8141 5 років тому

    Derek, Nice job explaining this problem!!!! What software/hardware do you use for your chaulboard?

  • @utuntupamed6224
    @utuntupamed6224 3 роки тому

    Thanks man have finally made it in physics

  • @colorgreens
    @colorgreens 14 років тому +1

    your hand writing is beautiful! :)

  • @redcamel7965
    @redcamel7965 8 років тому +1

    thank you very much for this great video, it really helped me all .

  • @iibornfighter
    @iibornfighter 12 років тому

    WOW you are the best!!! Way better the over rated khanacademy

  • @jioddon
    @jioddon 14 років тому

    your d bosss...... u deserve a grammy mi bosss

  • @PhilberthBundo
    @PhilberthBundo 5 місяців тому

    It's very helpful, thankyou for the video

  • @lonogugeadult
    @lonogugeadult 13 років тому

    @emmalainesmiles you'd use the equation y = yo + vo(t) + 1/2a(t^2) and plug in what you know for the vertical component to solve for t

  • @rangiroa100
    @rangiroa100 2 роки тому

    Hi Derek. I got a question. An object fall to the earth at 9.8 meter per second. If the vertical distance is 100 meters, then 100 / 9.8 = 10.20 seconds. It would take 10.20 seconds for an object to fall 100 meters. Your calculation showed 4.52 seconds. Can you explain the discrepancy ?

  • @TheOne-sp8vx
    @TheOne-sp8vx 2 роки тому +1

    Why is Y positive when it goes downwards? I always see people making Y positive upwards. Now this made me more confused😔

  • @RandomBoggoDude
    @RandomBoggoDude 10 років тому +1

    Nice vid, somewhere there is either a mistake in my books or with my interpretation of the formula. If I use the formula
    "delta x =[(Vf+Vo)/2*delta t]" i get exactly double your answer. That is if I use Vf as 0. Is using Vf as 0 wrong while working with projectiles or is the derivative formula I'm using wrong?

  • @derekowens
    @derekowens  12 років тому +1

    @804YankeeFan The buoyant force is very tiny, and is generally considered small enough to ignore. One could, though, include both the buoyant force and the air resistance in the calculations. The calculations get beyond the scope of this course, though.

  • @LeonardATF
    @LeonardATF 11 років тому +1

    Thank you I couldn't understand until I watch this

    • @gggg-gu2hl
      @gggg-gu2hl Рік тому

      Did you pass? It been 9 years

  • @AVerbene
    @AVerbene 13 років тому

    thanks to you, i am going to pass my physics midterm tomorrow

    • @gggg-gu2hl
      @gggg-gu2hl Рік тому

      Did you pass? It been 11 years!

  • @duanoor3061
    @duanoor3061 9 років тому +1

    thank you very much for this great video, it really helped me allot

  • @thepunisher1951
    @thepunisher1951 8 років тому +1

    Thank you very much. It helps me a lot.

  • @mdewolfe33
    @mdewolfe33 7 років тому +1

    Got it perfectly right! Thank you

  • @OmarSN93
    @OmarSN93 12 років тому +1

    thank you so much :) i solved it before you started solving it and my answer was the same as yours :D

  • @jojosh234
    @jojosh234 13 років тому

    @jojosh234
    the vertical distance should be at negative because it's going down to Y axis,

  • @EpicJelly
    @EpicJelly 9 років тому +4

    how is there no horizontal acceleration? the horizontal acceleration should be negative since it slows down as the object loses it's speed?

    • @derekowens
      @derekowens  9 років тому +6

      EpicJelly Yes, in reality it does lose some horizontal speed due to air resistance. If we neglect the air resistance, though, then the horizontal speed is constant, because gravity only acts in the downward direction, and does not speed the object up or slow it down horizontally. There are no horizontal forces, so there is no change in the horizontal speed. We could include the air resistance, but that changes the problems to a much more difficult problem. In this case we have made the simplifying assumption that air resistance can be neglected.

    • @EpicJelly
      @EpicJelly 9 років тому +1

      thanks a lot!

    • @ryanjustinmarantan8146
      @ryanjustinmarantan8146 8 років тому +2

      OMG TY FOR ASKING THIS QUESTION. AND THANK YOU FOR THE ANSWER, DEREK.

    • @jcrlaptoptrading
      @jcrlaptoptrading 6 років тому +1

      nice, thanks

  • @TheCarlosfgm91
    @TheCarlosfgm91 14 років тому

    Awesome! thanks for the help! please keep on making physics videos, they're a ton of help! 5stars!

  • @rockster16
    @rockster16 14 років тому

    @RuthBuzzzzz It would be negative, but when you square anything its always the absolute value of that, so the negative or positive wouldn't matter

  • @aneesaattaullah3554
    @aneesaattaullah3554 10 років тому

    I chose up as positive, meaning gravitational acceleration is negative but i get a different answer, -4.52 seconds and -21 m/s ...why is it so?

  • @panchovilla5400
    @panchovilla5400 4 роки тому

    HI! IN THIS CASE THERE ARE TWO VELOCITIES TO BE CONSIDERED. ONE THAT IS ZERO (THE ONE GOING DOWN). AND THE ONE THAT YOU FOUND OUT. THIS VELOCITY IS """"CONSTANT"""" AND GOING HORIZONTALLY!!!!!!!

  • @HienNguyen-jv1px
    @HienNguyen-jv1px 11 місяців тому

    thank you so much ! this was so easy to understand and it also makes sense!!!

  • @omsnet63
    @omsnet63 10 років тому

    My only doubt is that if acceleration horizontally is zero the projectile should keep moving in the same direction (if its velocity is constant ) then why does it stop? ( i m sorry if its 2 obvious)

  • @heavenz94
    @heavenz94 11 років тому

    i think it was a lil bit too complicated. simply just find v initial first which is root 2*g*h. then use then formular v= u + at to get ur time. then substitute for speed = distance/time

  • @Cleopatra0629
    @Cleopatra0629 2 роки тому

    I have the first problem as my assignment and im confused because the process and the labels used are different TT

  • @jasonramkhelawan4859
    @jasonramkhelawan4859 7 років тому

    vo in the horizontal is 21m/s what about the initial velocity shouldt it be vox=cos(angle)*vo therefore the angle shoul have been given....just saying

  • @davidbuckingham6594
    @davidbuckingham6594 3 роки тому

    Hi hope you won't mind me asking but I am a physics teacher and I'd like to do this kind of thing to support my students remotely during this pandemic.. I am not trying to compete with you but I wondered if you could tell me what hardware / software you use to produce these high standard tutorials. No substitute with physics to being able to write equations draw diagrams etc. Many thanks for any help you can give.

    • @nikitamalkov6160
      @nikitamalkov6160 3 роки тому

      You need a graphics tablet (or Apple Pencil if you have an IPad) and any type of software like OneNote or even Photoshop

  • @josuekoenig1723
    @josuekoenig1723 5 років тому +2

    I watch these because my teacher is bad

  • @thejavellanas
    @thejavellanas 10 років тому +1

    you explained very well. :)

  • @user-mm6vm2kc6p
    @user-mm6vm2kc6p Рік тому

    Why the the acceleration is not negative if it's going horizontally?

  • @slamreaper2269
    @slamreaper2269 4 роки тому

    if the origin is 0 then why horizontal displacement isn't -100m?

  • @804YankeeFan
    @804YankeeFan 12 років тому

    @derekowens So, I have a last question I was wandering about. So are satellites orbiting the sun with the Earth while they are orbiting the Earth? Does this cause the Earth to be an inertial reference frame when calculating its orbit?

  • @darkforcekiller
    @darkforcekiller 6 років тому

    You could solve this much faster just by setting the horizontal formula (free-fall) equal to the vertical formula (kinetic) and plugging in your variables.

  • @user-nj5ci1tf6i
    @user-nj5ci1tf6i Рік тому

    I am quite confused,why is the initial height of the ball vertical zero yet it is thrown from a 100 m heigh building?😢

    • @derekowens
      @derekowens  Рік тому

      The setup could be done a few different ways. For example, you could call the height at ground level zero, and the height at the top of the cliff 100, and then up would have to be the positive direction. In this case, I think the problem is slightly easier to set up with down being positive, and the starting height is zero. Hope that helps!

  • @harkendoich2
    @harkendoich2 12 років тому

    If its motion is influenced by gravity only and gravity pulls straight down, why does the projectile travel 95m?
    I mean, if you dropped a bullet off the edge of the cliff it would fall straight down, but if it was accelerated out of a gun it would travel several hundred metres due to the acceleration.
    So in theory this projectile in the video must've had acceleration as opposed to just dropped off the edge?

  • @RonaldTani
    @RonaldTani 3 місяці тому

    Thank you job well done ✅

  • @Stinglikeabee625
    @Stinglikeabee625 14 років тому

    i do not understand why the acceleration is positive in this problem! i thought because of gravity pushing down 9.8 would always be negative.

  • @anuurcc35
    @anuurcc35 13 років тому

    @ derekowens; When finding the initial horizontal velocity, should time be doubled @ 7:21 so that it account for the whole horizontal time. So instead of 4.52 should it be 9.04. Can anybody else see what I'm talking about as well?

  • @randys2669
    @randys2669 10 років тому

    Can't you just use a single equation?
    because t=x/vcos(θ)
    y=xtan(θ)-gx^2/2v^2cos^2(θ)
    tan(0)=0 so:
    y=gx^2/2v^2cos^2(0)
    cos^2(0)=1 so:
    y=gx^2/2v^2
    100=9.8((95)^2)/2v^2
    If I'm not mistaken.
    Simply state time in terms of x. "x" velocity never changes in this kind of system after all!

  • @kareemkourouma3976
    @kareemkourouma3976 12 років тому

    why is the intial velocity horizontally 0? wouldnt it need some velocity once it reached the edge of the cliff to keep moving horizontally.

  • @rebeccacandranitasetiawan4721
    @rebeccacandranitasetiawan4721 9 років тому +3

    Isn't the horizontal is the x?
    and the vertical is the upward / the y?
    I'm confused.

    • @coleader206
      @coleader206 6 років тому +1

      Yup. You are correct.

    • @diwakarsingh5466
      @diwakarsingh5466 5 років тому

      No you treat them as different the only thing common is the time which is to be calculated via downward component and horizontal component remains unchanged so use the calculated time in it I did it the other way used time outta accelerate motion and utilized it is horizontal

  • @brentsmith8552
    @brentsmith8552 10 років тому

    Thanks for posting. But, why did you derive t=squ 2(y)/a??? there was no reason to do that. the original y=1/2at^2 was fine.