Kinematics Part 4: Practice Problems and Strategy

[@5uperDetective]

bruh you taught me kinematics in about 40 minutes worth of videos... compared to 3 weeks worth of lecture that I was still iffy about. You should really be in the classroom man. Educators need to stop overcomplicating these concepts and teach them like you.

[@craigkhumalo6854]

thats so true lol

[@russellerocido7897]

teachers are meant to reach a certain time quota for teaching which is kind of the reason why they drag stuff on when they teach which makes it complicated. not their fault really. but Dave is really on another level

[@shawshaneremollo3315]

I also learn kinematics from him in 1 hour compare to a 3 weeks worth of lecture

[@wislanenoel2955]

Also he seems like he enjoys teaching. Our profs are a bunch of researchers they force to teach they have no passion for education.

[@yourmom-oy7ds]

Facts

[@zahidimuhammadnasrulhaq8678]

thank you dave , i was crying all these time because i failed my examination since i didnt understand a thing . but your videos make everything clear for me. i wish you have a really nice life out there :)

[@akshayreddyatchi1971]

failure

[@netad7771]

@@akshayreddyatchi1971 Why are you so sad in your life you have to spread your sadness to others??

[@lordth7200]

@Akshay Reddy Atchi this is why your dad left you.

[@sanajindal9644]

lmao same but i still dont rly get it😭😭

[@thomasaskew1985]

I haven't solved problems like this since 1970. That was 9th grade Science for me. You covered in minutes what took me weeks to learn as a 13-year-old.

[@JohnDoe-ht2tu]

Dave, if I could send all my tuition money to you I would do it in an instant. You're so much better at teaching than any "professor" with a PhD.

[@Occ881]

Send a little bit,it's not necessarily your tuition fee

[@aronabraham4657]

Whoever came up with the invention of recorders is a genius. I don't have to tune in to classes at school as much cuz I have an online textbook, a few different youtube channels (that's only youtube), and like a few other resources for a single hw assignment. I know everyone has access to this but just wanted to say thanks formally.

[@EREN-he9jl]

wassap

[@TheRolvaag]

You are excellent at explaining concepts in a simple manner, thank you for putting these out

[@akshayreddyatchi1971]

not at all he uses complex thing why in the world will he use v sub i instead of u. Cuz he is a professor

[@Alex-ns6hj]

@@akshayreddyatchi1971 what would u represent? why u? v_i is the same as v_0, it just denotes your initial velocity... the only u I know has a good representation for is u-sub for integrals lol

[@lokeshchandore7027]

I love the intro song and animation

[@zakiyatdjabakatie7071]

lol me too

[@landofmyth221]

Same 😂💕

[@landofmyth221]

I say that intro song all day at home 😂

[@VndNvwYvvSvv]

It makes me cringe and I skip it so people don't think I'm watching videos for elementary school, because I know they won't listen to the organic stereochemistry or physics. Lol

[@UnrealogyTutorials]

He do be knowing a lot about the science stuff tho

[@DonStefMutileni]

Writing engineering physics tomorrow and confidence is rocket high cause of this video... 😊

[@Occ881]

You graduated huh?

[@DonStefMutileni]

Yes 😅 omg I remember this comment!!! 🤣

[@gadeeecasty9073]

Congrats!

[@birasatdahal8181]

One of the best lecturer of all time, I am quite impressed by the way he teaches

[@rydertwo2151]

bro when i was a senior people looked at me like a God because i perfect the exams. cant thank u enough, man. currently taking civil engineering in college now.

[@elliejohnson2786]

In case anyone missed it, and it wasn't explicitely obvious - The care package/helicopter example includes a piece of information that may not be immediately obvious. When the care package is dropped, it maintains the velocity of the helicopter, and so will have the same velocity of the helicopter. This is one of those things that isn't actually explicitely told to you, but that you can figure out rather quickly.

[@helloAM2]

The visual aids and seeing things in actual motion really help. Shout out to the graphics team.

[@castlesinfo6049]

learning calculus makes this a lot more intuitive.

[@hidetsuguhiraki2008]

You know what teachers should teach her/his students. You are a great teacher, Sir.

[@abdoulazizdabo9064]

You really a gift to the world. Thanks professor

[@Reena-maheshwari.803]

I am a proffesional expert at NASA Agency. I always used to show your videos to my children. Me and my team trying to solve SpaceX kinematics problems to make a future Speedy (Light of speed) Satellite to find more about Universe.

[@nathanhynes8063]

thanks professor Dave! Ive bought the text book for my physics unit and re watched my lecture twice. Now i finally understand after watching your videos

[@mariasalvenia35]

2:37 why is x = 1.28m?

[@sloojey]

This 100% should have been the first video

[@Obliviousovertimer17]

if only the test questions were this simple, i would have scored full

[@justgocoolla]

yall know this guy is good when there are no ads in his videos

[@landofmyth221]

Came here from my other KZbin account to click that like button once more for 1k 😍🎉

[@akshatjindal1508]

When solving projectile questions, I was confused about time in horizontal and vertical component. But after reference from your video, got everything clear

[@annieli3258]

This has helped me so much! I don't have to go to class feeling like an idiot anymore

[@nikbirkundi5223]

“I love you”

[@user-fh2rw9zh8g]

Hey love your videos! Just a note for the comprehension question. Actually if we have to calculate the time in air we should be given that the ground (x'x) is still there till end. Because if he was on a hill for example then the t total isn't equal to 2tmax

[@zakiyatdjabakatie7071]

Also thank you, I understood a lot to the point that I am actually able to question answers that seem off. Thank you, Sir.

[@amandeepbaghiana4510]

1:08 The equations aren't labeled correctly. the first equation "Vt" is supposed to be Vf (velocity final) and in the second; "Xt" is supposed to be Xf (position final)

[@ProfessorDaveExplains]

Same thing. The t in subscript means at some designated time t.

[@helviitana]

Thank you professor Dave!! 😊😊 Bless you

[@mekbebseyfu9371]

you're the best professor i have ever seen

[@davidrohanadorna8792]

GUFSA Given Unknown Formula Substitution or Solution Answer

[@Spark3r]

Hey dave, really enjoyed the video and was helpful but its good to note that usually we do vy and vx in physics to tell the difference between the velocity vectors. it helps a little bit, if you ever update this video it would be nice to clarify that next time for easier use.

[@Namjoonsthighs]

1:35 There is actually an equation for this, t = u/g . When I used this I have gotten them same answer but in a -ve form. May I know why this formula doesn't apply? Or did I use the wrong values?

[@ericard4165]

at 3:33, i think u shouldn’t double 0.51s to get 1.02s. I think we should do that in two different part. First we calculate time for reaching maximum height, we indeed get 0.51s . But now, the velocity is 0, and the ball only due to gravity, so we just consider this as you throw this ball from cliff of 1.28m height and see how soon will it hit the ground. So 0m=1.28m+1/2(-9.8m/s^2)t^2 then we easily get t^2=1.96 we take root from both, we get 1.96s, so the first 0.51s plus 1.96s is 2.47s instead 1.02s I don’t know if I am right, this is my own opinion

[@ProfessorDaveExplains]

you certainly can do that, it's just more work. the time it takes to go up is the same as the time it will take to go down, so it's just a shortcut.

[@randallpetroelje3913]

Believe you and me- I also had to make calculations about water balloons, paper airplanes, and fireworks.😂👍lots of fun and no blown off fingers. Thanks again for your show.

[@joshuadilao1496]

I dont know if its just me but 2:38 I got 5.4 as an answer for maximum height instead of 1.28

[@rats1740]

same here

[@aveinmovil]

Try to do the operation by hand. If the mistake doesn't pop up for you ask again.

[@fanticer]

Your lectures are superb💕💕💐💕

[@adi01244]

congrats, you've got π subscribers!!

[@wakuwaku3190]

it took me this far to understand projectile motion. THANK YOU SIR! ❤

[@CaptainObvious0000]

easily doable without explicitly using formulae as well. initial velocity being 5m/s and decreasing by about 10m/s², v reaches 0 in 0.5 seconds. this time is spent moving at a velocity of between 0 and 5m/s, deceleration happens linearly. average speed upwards is 2.5 m/s. *0.5s is 1.25m.

[@ranisjohnclienta.1854]

Time: 1.8026 DisplacemeDisplacement:31.866 Is this correct?

[@udaypersonal8434]

double the time

[@madibrown84]

bout to tackle my very first AP physics test. wish me luck !

[@nancyxi]

What did you get?

[@nancyxi]

Good luck if you're taking more..:)

[@Cap.doc111]

The conclusion of the whole video is in the first 40 seconds : practice a lot

[@anthonyrichard1365]

Thank you very much, Professor Dave!

[@tejsukumaran4905]

you're the goat professor dave

[@rohitsurwase5284]

Totally clear concept video .

[@saturdayBees]

❤❤❤❤❤❤❤ This is the best .. thank you sooooo much..

[@chongyeeyun4899]

Video is interesting and creative with many easy picture and word

[@mariasalvenia35]

thank God! I now know what equation to use

[@kujirakan9537]

this video is the best of the best

[@nickdicerbo6361]

Hi Dave, it possible to find the max height using this equation: Vy^2= Voy^2 -2g(Y-Yo) where Vy=0 to solve for (Y-Yo). Vy=vertical velocity (0m/s) Voy= intial vertical velocity (~17.67m/s) g= vertical acceleration (9.8m/s^2) Y-Yo= vertical displacement (solved to be 15.94m) Then plug the value of (Y-Yo) into this equation and solve for time: Y-Yo= -.5gt^2+Voyt to solve for t and multiply by 2 t=time (solved to be 1.77s and 1.8s) To solve for t, i used the quadratic equation but got 2 similar answers. the first being 1.83 and the second as 1.77. Why did i get 2 possible answers that were so similar to eachother (and to the correct value)? Or is this the incorrect way to solve for t?

[@joy4467]

4:29 here why a is -9.8 m/s^2

[@crocopie]

Hi there. 4:37 may not be a good example in real life because dropped packages must be parachuted while airborne so that the packages would not be be damaged. A better example would be releasing bomb 💣 into an enemy structure :D.

[@alex_ramjiawan]

Couldn't you do the second problem using ∆y = v₀t + ½at?

[@akashpoudel571]

So nice professor dave... Hats off

[@scenify3758]

great video dave!

[@abdelhamidahbane6322]

in the ending comprehension test, Why did you consider the time calculates as a peak time and then multiply it by two ??? isn't it itself the whole hanging time ? I am confused !!

[@abdelhamidahbane6322]

Oh NO NO I got it now, I was wrong. I used the displacement equation instead of the velocity equation....it makes sense now, THANKS Prof, you are the best

[@FreyaChristina]

Hello Professor Dave, I read that the acceleration due to gravity during a free fall is 9.8 but When it is thrown upwards its negative

[@ProfessorDaveExplains]

it's always negative! because the acceleration occurs in the negative direction, towards the earth.

[@EREN-he9jl]

that is because gravity is negative... but since it is thrown upward WHICH IS POSITIVE .. so basically.. negative times positive is negative.. that is why ..

[@abegailcamacho6003]

Can someone please explain to me how (0 m/s)² = (5.0 m/s)² + 2(-9.8 m/s²) turn into x = 1.28 m?? I watch the video a couple of of times but still can figure it out how did that happen......

[@jamaicanipot-nipot5210]

same prob haha

[@gabrielwongso2309]

(5.0 m/s)² ÷ 2(9.8 m/s²) 👍

[@alexishunt3752]

I used the equation change in y = (viy)(t) + 1/2(a)(t2) and used the quadratic equation to solve for t = 4.928s. Why didn’t this way work?

[@sarastemkar7835]

this equ is for dist/displacement equ contains two unknown if you are solving for time

[@noraunisyafiyaabdulhalim4701]

Simple and easy to understand

[@MG22991]

Thank you so much for this video.🙂

[@gurgferguson292]

1:36 am studying for Kinematics test, feeling better

[@nguyentuanlinh4584]

can i have a question? I always wonder why a is negative when a ball is thrown upward?

[@ProfessorDaveExplains]

acceleration due to gravity is always downward, which is the negative direction

[@nguyentuanlinh4584]

@@ProfessorDaveExplains Thank you very much for the useful lesson.

[@online_class_with_ajibola]

What can I say? Thank you. Thank you and Thank you

[@justinbeiberdrew1145]

good explanation.....

[@shoosz7644]

Hey Dave please use miles as well as kilometers. Thanks.

[@ProfessorDaveExplains]

scientists only use the metric system!

[@DimuthuYapa]

Thank you, sir.

[@Attalla-t9b]

6:09 How did you get the total hang time? Any reason why we should multiply it by 2? Edit: ig bcs it goes up (peak), and then goes down to 0 (position initial) again. That's why it's multiplied

[@Attalla-t9b]

6:07 wait... 25 sin 45 isn't 17.7, netiher is 25 cos 45. Am i missing something here?

[@ProfessorDaveExplains]

it is that though

[@Attalla-t9b]

@@ProfessorDaveExplains nvm you're right on this one lol (google search automatically measured sin & cos in radians when it should've been in degrees)

[@gamingdude7959]

25 sin 45 is 25/√2 which is approximately 17.7. And so on.. He rounds it up to make calculation easier

[@GermaniaceezTV]

congrats to 1M subs

[@DaaliElizabethh]

Keep it up.thanks

[@MetalAngelOfficial]

Thank you sir

[@yosefrabinow9788]

thanks so much, your videos saved me from failing my physics regent!

[@garyhenderson5256]

i need your help with what math to use to calculate the ballistics for a basic artillery game i’m wanting to write in BASIC. The variables are how many bags of powder, angle of the barrel, wind direction and wind speed. The playfield is a very basic random 2 dimensional terrain made up of a line drawn across the screen and random placement of your fort and the opposing fort and you take turns firing back and forth guessing how many bags of powder and what angle to point the cannon

[@navenaramachendran8997]

Good explanation

[@samij8639]

Why horizontal and vertical velocities 17.7 instead of 25 as it is given to us?

[@ProfessorDaveExplains]

you have to do the trigonometry! the calculation is shown. check out my tutorial on projectile motion for a more thorough explanation.

[@avililies]

I hate that when solving the problem is skipping some important steps, like how did you get that answer while mine is nothing like that?? What did you do first?? Did you multiply then yada yada yada.

[@davis4537]

One the first problem, can someone explain how he is getting 1.28m. I keep getting 5.4.

[@kennethgabriel2234]

divide the initial velocity with the acceleration after multiplying it by 2

[@itssohotinhere4615]

i keep on getting 0.26😭😭

[@itssohotinhere4615]

OH THERES SQUARED ON THE FORMULA MB

[@itssohotinhere4615]

but like how did the sign become m? like i get it we r looking for the dastance but like when u manually do it, it makes me cancel both of the m/s^2 of the numerator and denominator?

[@cameronketola250]

At 4:35 how did you get 4.95

[@Horologica]

He used the quadratic equation to find T -120 = 0t + 0.5 (-9.8)t^2 0.5(-9.8)t^2 + 0t + 120

[@nicbaeten]

How to calculate the corner that I have to shoot with a air rifle that the pellet escape the barrel with 300m / sec and has a weight from 0,49gr. until it fal back in to the barrel and not 20m further by the neighbors Because the turning speed of the earth? Traveltime about 5 sec.

[@godot5643]

when will you upload on the topic of quantum mechanics..?

[@ProfessorDaveExplains]

gotta finish classical physics first, but then it's modern physics right after that! so i would say in about three months.

[@imwmt]

Thank you

[@vionamarieVelasco]

shortcut for time flight timeflight = [Vi•sin(theta)/g] 2

[@shawqial-zewar6215]

thank you... ❤

[@moiseslobopvh]

Hello teacher. How can I find the shooting angle of a ball to hit a basketball hoop, if I have the speed, gravitational acceleration and vertical and horizontal distances? I can't deduce an equation to find the angle when the target is above the launch point.

[@Thesaviorsway]

I was able to get time but my error for displacement was half using average velocity formula. I then realized you multiply time by velocity in x direction to get total distance if velocity is the same. if velocity changes from initial to final you take the average and multiply by time to get distance.

[@sturmfrey]

so according to the workings, the time taken to reach the peak is always proprtional to the time taken from the peak to hit the ground. therefore, if asked for hang time, we can always just calculate time taken to reach peak and x2?

[@ProfessorDaveExplains]

If start and end point are at same height yes.

[@sturmfrey]

@@ProfessorDaveExplains thank you sm

[@micmaci9343]

Why total hangtime is equal 3.6s in checking task ?

[@angelacacanog4979]

why is the answer incorrect when i input it on my calculator?

[@jonesnamakhwa9281]

I thank a lot my professor I get something

[@afa4770]

Good explanation thanks a lot

[@norjanajalel9077]

Life saver 😌😌😌

[@zahirul9916]

The "Lots of practice" is useless when you have an exam at 9am and it is 5.13am right now...

[@MsPslater]

can you do some examples and show how to do the calculations without a calculator?

[@inspiringer6418]

I have to do a problem to find the initial velocity but I don't know the acceleration either. All I know is that the final velocity is 0 and the displacement is 60 meters.

[@MrBits_0]

how did you get the 4.95s?

[@ramkumarganesh2453]

While finding the distance travelled by the ball which is thrown upwars.. shouldn't the gravity 'a' be +9.8 m/s?? if I'm wrong pls explain me!!

[@ProfessorDaveExplains]

but acceleration due to gravity pulls objects downwards, which is the negative direction!

[@hamzarawi1805]

@@ProfessorDaveExplains but in the last question the box was falling so why was the acc negative since it's in the same direction of free fall

[@ProfessorDaveExplains]

acceleration due to gravity is -9.8 m/s^2, this is constant and has nothing to do whatsoever with the motion of any particular object

[@megfouxx3166]

@@ProfessorDaveExplains when you found t=0.51s why didn't the negative acceleration affected the answer i mean it should have been t= -0.51s If am wrong plz crrect me my exam is next week.

[@ProfessorDaveExplains]

@@megfouxx3166 think about what you're saying there! You're implying that gravity causes things to go backwards in time. Does that make sense?

[@noooby1324]

thank you so much

[@Mellow429]

If teachers/education system taught in this way(simpler, quicker, basic cartoons, straight to the point) Everyone would have a college degree bc I feel school/college/education would be tremendously cheaper and easier to access which would make our economy so much better. I don't understand our "system"