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Physics projectile motion problem +k

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kung_powpow
Posts: 1990 - Karma: 3,671
Only did half a test today so I wrote down the problems but still can't do this shit for my life. Help a homie out! +k

An object is shot off a 15m high cliff going 20 m/s at 45 degrees. Find the final velocity in the Y direction.

Dec 5 2013 9:03PM
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Dr.Dickless
Posts: 2620 - Karma: 1,392
http://www.physicsclassroom.com/class/vectors/u3l2f.cfm

I was going to do your specific problem, but im really lazy, this site should help you out a bunch
they lay everything out pretty simply



Dec 5 2013 9:07PM
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bighomieflock
Posts: 2040 - Karma: 2,445
Click for larger image

Memorize these equations and then use whichever one fits the variables you have and need.

If you can't solve the problem with one equation then you'll have to use 2 of them. In this case you can usually solve for time in the y direction since its equal in both the x and y axes.
Dec 5 2013 9:10PM
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SFB
Posts: 8895 - Karma: 26,352
purple
Dec 5 2013 9:14PM
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YoungChristmas
Posts: 1066 - Karma: 2,110
This will help

http://www.avon.k12.ct.us/WebCurriculum/Science/Physics/Unit%2004%20-%20Vectors/Background%20Reading%20-%20Vectors%20and%20Projectile%20Motion.pdf
Dec 5 2013 9:35PM
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coling
Posts: 1086 - Karma: -3
At 45 degrees that means the y component of the velocity is 10 m/s and the x component is 10 m/s. since your only looking at the y component just assume the projectile was shot at 10 m/s straight up. The max height of the projectile will be 20 meters because g will slow it down to 0 m/s after 1 second because g = 10m/s^2. So you can look at it as a projectile falling from 20 m. Use d=1/2at^2 to find the time it will be falling which is 20= 5t^2 , 4=t^2, t=2 seconds.
Then use v=at so v = 10m/s^2 x 2 s so v=-20 m/s in the y direction.
Dec 5 2013 9:53PM
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coling
Posts: 1086 - Karma: -3
Forgot to say that the max ht will be 20 m because after 1 second going up at 10m/s, the projectile will have risen 5 m because its average speed when rising will be 5 m/s.
Dec 5 2013 9:56PM
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coling
Posts: 1086 - Karma: -3
Sorry fucked that up i havent done this in a decade. Y comp of v is v sin 45 = 14.14

To avoid having to use the quadratic formula or a graphing calc, split up the problem. First find the max ht of the object by using v1 + at =0
So 14.14m/s - 10m/s^2 x t = 0 so t= 1.414
Max ht = 1/2v1t +initial ht. so max ht =1/2x 14.14m/s x 1.414 + 15 m = 25m
Now use d=1/2at^2
25m= 5t^2
5m=t^2
T= 2.24 (time it spends falling from its max ht)
Now use v = at. So v =2.24s x -10m/s^2 = -22.4m/s in the y direction
Dec 5 2013 11:11PM
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ALMIGHTYSOSA
Posts: 2800 - Karma: 2,102
haha we did a half test to on projectile motion today too.
Dec 5 2013 11:15PM
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KingGeedorah
Posts: 890 - Karma: 1,576
OK, so draw a right triangle with a 45 degree angle, and a hypotenuse of 20m/s. Then, both of the other sides will equal 10sqrt(2) or 14ish. Then just do the rest as iff the object is being thrown straight up at 14m/s.
Dec 5 2013 11:24PM
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coling
Posts: 1086 - Karma: -3
The total air time is the time the object spends rising (1.414 s) + the time it spends falling (2.24 s)
=3.65 seconds.
So plugged in to the equation d = v1t + 1/2at^2
You get -15 (the net distance the object falls) = 14.14 x 3.65 + 5 x 3.65^2 which checks out
Dec 5 2013 11:27PM
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coling
Posts: 1086 - Karma: -3
Sorry the last line should have been
-15= 14.14 x 3.65 - 5 x 3.65^2
Dec 5 2013 11:29PM
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whoa-dere
Posts: 10596 - Karma: 7,103
physics was my shit back in high school! i got the highest test score in the entire grade multiple times and the nerds were mad
Dec 5 2013 11:30PM
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MontanaMountains
Posts: 385 - Karma: 699
Copy the question into google and about 90% of the time someone will have already asked it on Yahoo Answers and if not there is one very similar to it
Dec 5 2013 11:33PM
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coling
Posts: 1086 - Karma: -3
Hs physics was so easy it was rediculous
Dec 5 2013 11:36PM
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coling
Posts: 1086 - Karma: -3
I gave a better answer than he could find on google
Dec 12 2013 8:39PM
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chicken
Posts: 6843 - Karma: 2,123
no you didn't. you took a bunch of unnecessary steps. the question asked for a final velocity and gave you an initial velocity and an initial height.
Dec 13 2013 1:03AM
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BeefiestExpert
Posts: 2804 - Karma: 3,277
I could of sworn there is one more kinematic.
Dec 13 2013 1:08AM
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whoa-dere
Posts: 10596 - Karma: 7,103
the big 5
Dec 13 2013 1:11AM
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chicken
Posts: 6843 - Karma: 2,123
there are four equations. Kind of a waste of time to memorize them though. Just remember that v=dx/dt and a=dv/dt and you are golden.
Dec 13 2013 1:23AM
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BeefiestExpert
Posts: 2804 - Karma: 3,277
Well i wouldn't say a waste of time exactly. But your right i mean you will mostly only really need to memorize thevot+1/2at^2 equation. The rest you will barely use.
Dec 13 2013 2:04AM
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coling
Posts: 1086 - Karma: -3
Are you that fucking stupid? Read my whole post fuckstick!
Dec 13 2013 2:06AM
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coling
Posts: 1086 - Karma: -3
Why dont you expound on that jackoff?
Dec 13 2013 2:08AM
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coling
Posts: 1086 - Karma: -3
Like i said, lets see you strut your stuff! Show us how your 2 special equations will lead you to the answer i got! Lets see it my child!
Dec 13 2013 2:14AM
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chicken
Posts: 6843 - Karma: 2,123
Read what? you took a bunch of unnecessary steps to solve a one-liner.
Dec 13 2013 2:21AM
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coling
Posts: 1086 - Karma: -3
Actually i didnt. If you wanted to do it in one line, you would need either a graphing calc or the quadratic formula. I showed how to do the problem without them. Youre pretty stupid man. Why dont you show us all how stupid you are by trying to solve the problem your way and fukn failing miserably?
Dec 13 2013 2:28AM
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chicken
Posts: 6843 - Karma: 2,123
no. you can literally plug the values into the kinematic equations provided above and get the answer immediately. No quadratic formula or graphing calculator necessary. If you take g=10 then you wouldn't even use a calculator.
Dec 13 2013 2:38AM
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coling
Posts: 1086 - Karma: -3
Show us how fuckstick? Haha youre talking trash and you cant even do this simple fucking high school problem ya retardddd
Dec 13 2013 2:40AM
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coling
Posts: 1086 - Karma: -3
Haha thats what i thought! Youre talking out of your fat fucking ass and you dont actually have a clue how to solve the problem. Go back to the trailer you live in, fuck your sibling and cylry yourself to sleep you dumb fuck
Dec 13 2013 2:48AM
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chicken
Posts: 6843 - Karma: 2,123
oh for fucks sakes. give me a minute then.
Dec 13 2013 2:49AM
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coling
Posts: 1086 - Karma: -3
Whats wrong? Did you figure out that you cant do it without a calc or the quadratic formula unless you split it up yet? Ya dumb fuck
Dec 13 2013 2:55AM
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chicken
Posts: 6843 - Karma: 2,123
Click for larger image
Dec 13 2013 2:57AM
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coling
Posts: 1086 - Karma: -3
Haha thats what i thought. Cant even write it out on your computer. Fucking loser you dont have a clue what the fuck youre doing
Dec 13 2013 3:06AM
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chicken
Posts: 6843 - Karma: 2,123
like i'm gonna bother to typeset that in LaTeX so I can show a troll I can do a 10th grade physics problem.
Dec 13 2013 3:09AM
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Bensun
Posts: 480 - Karma: 1,654
so much buttt hurtin its crazy.
Dec 13 2013 3:10AM
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coling
Posts: 1086 - Karma: -3
You cant do the problem. Youre a fuckin idiot and a liar. Do it out on the computer or youre a total joke
Dec 13 2013 6:34AM
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El_Barto.
Posts: 11661 - Karma: 24,354
dolan lol
Dec 13 2013 8:49AM
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TOAST.
Posts: 7481 - Karma: 36,054
Vf^2=vo^2+2a(xf-xo)
Vo=20sin45
A=9.81
Xf=0
Xo=15
think thats right.
Dec 13 2013 9:49AM
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chicken
Posts: 6843 - Karma: 2,123
I love how up until you started saying this shit you weren't even trolling. You legitimately thought that this problem couldn't be solved using one formula.

Derive the equations of motion using Lagrangian mechanics, or you are a total joke. If you are going to waste time doing unneccesary stuff, at least do something that's cool.
Dec 13 2013 1:10PM
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krum
Posts: 79 - Karma: -167
its called Gravity, you have to understand g-force
Dec 13 2013 1:16PM
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yuck
Posts: 8384 - Karma: 2,090
youre quickly becoming the worst member on this site

not even in a good troll way either. I like good troll accounts usually but youre just like, really bad at that and have contributed nothing but shit to the forums since you popped up

you have nothing to be proud of, you are a terrible member and probably a terrible person in real life too. figure your shit out man. and im not remotely mad or upset about this, so you cant really consider this as a "troll win" either. im just shaking my head at how miserable you are at everything and how terrible your interpersonal skills are
Dec 13 2013 2:34PM
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coling
Posts: 1086 - Karma: -3
Dude dont be mad because your wrong, do the problem your way or shut the fuck up
Dec 13 2013 5:33PM
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coling
Posts: 1086 - Karma: -3
Are you not rustled!
Dec 13 2013 5:34PM
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coling
Posts: 1086 - Karma: -3
And yeah, i am a terrible person in real life. Does that bother you haha
Dec 13 2013 5:36PM
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coling
Posts: 1086 - Karma: -3
Are you mad that an opiate addict is seen solving an easy physics problem that he forgot how to do and claims he did it on paper and took a blurry screenshot of. Im willing to bet my sats and iq were higher than yours and his so i really dont have the prerogative to give a flying fuck what you two think of me. Cheers!
Dec 13 2013 5:40PM
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coling
Posts: 1086 - Karma: -3
By he im referring to chicken
Dec 13 2013 5:50PM
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AT-AT
Posts: 3281 - Karma: 3,256
OP, everything that coling posted in thread is horseshit. PLEASE disregard any sort of "Intellectual" concept he has spoken of.
Dec 13 2013 6:28PM
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AT-AT
Posts: 3281 - Karma: 3,256
these are all you need to solve the problem.

initial y velocity = 20sin45
initial x velocity = 20cos45
a 9.8 m/s or 32.2 f/s
distance traveled is the height of the fall
Dec 13 2013 6:30PM
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coling
Posts: 1086 - Karma: -3
O really? Are you too stupid to follow my fucking logic?
Dec 13 2013 6:33PM
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coling
Posts: 1086 - Karma: -3
And you dont even know how to do the problem you fucking poser, otherwise, you would do it for us, ya towel
Dec 13 2013 6:34PM
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coling
Posts: 1086 - Karma: -3
You can use the middle equation but you need either a calc or the quadratic formula
Dec 13 2013 6:38PM
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