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Skiing Physics Homework!

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Adamskinick
Posts: 3353 - Karma: 126
YO BITCHES I GOT A PHYSICS PROBLEM WITH SKIING. I WAS SO EXCITED GOTTA SHARE IT WITH You. if u get the answer tell me!

A 65 kg skier starts from rest at a height of H = 20 m above the end of the ski-jump ramp (Figure 8-39). As the skier leaves the ramp, his velocity makes an angle of 28° with the horizontal. Neglect the effects of air resistance and assume the ramp is frictionless.


Fig. 8-39
(a) What is the maximum height h of his jump above the end of the ramp?
m
(b) If he increased his weight by putting on a backpack, would h then be greater, less or, the same?

the same (I GOT THIS PART ITS THE SAME)
greater
less
Turtle: Cmon guys get dates, it'll be like Prom! Eric: So I guess that means you won't have a date
Turtle: Fuck you guys, I told you 10,000 fucking times, she had food poisoning!-Entourage HBO
Jan 27 2005 8:13PM
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Adamskinick
Posts: 3353 - Karma: 126
they should made the fool do a cork 7, that woulda heated up the problem a little
Turtle: Cmon guys get dates, it'll be like Prom! Eric: So I guess that means you won't have a date
Turtle: Fuck you guys, I told you 10,000 fucking times, she had food poisoning!-Entourage HBO
Jan 27 2005 8:14PM
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CrazedSkier1080
Posts: 3357 - Karma: 66
i dont understand any of that jibberish, so im askin my friend whos wicked smaht!
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Jan 27 2005 8:16PM
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cLyOnS_45
Posts: 1072 - Karma: 10
11.84289474m perhaps?


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Jan 27 2005 8:23PM
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Adamskinick
Posts: 3353 - Karma: 126
nope, i get 2 more tries. help please!
Turtle: Cmon guys get dates, it'll be like Prom! Eric: So I guess that means you won't have a date
Turtle: Fuck you guys, I told you 10,000 fucking times, she had food poisoning!-Entourage HBO
Jan 27 2005 8:26PM
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dan.b
Posts: 866 - Karma: 10
b) he wont be able to do it a second time cause he will kill himself on that flat landing...
'Moi c'que j'propose c qu'on envoye chier l'monde, on leur paye une criss de traite'
Jan 27 2005 8:45PM
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dan.b
Posts: 866 - Karma: 10
how the fuck do we calculate the speed he have at the beginning of the jump? cause when you know that you can use y=y0+v0y*t-1/2*g*t^2...
'Moi c'que j'propose c qu'on envoye chier l'monde, on leur paye une criss de traite'
Jan 27 2005 8:52PM
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switch_9
Posts: 876 - Karma: 10
^i will tell you. MATH SUCKS!!!



'WHAT THE WTF?!?!!?' -Armada420
Jan 27 2005 8:55PM
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dan.b
Posts: 866 - Karma: 10
or you suck at math?
'Moi c'que j'propose c qu'on envoye chier l'monde, on leur paye une criss de traite'
Jan 27 2005 8:57PM
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switch_9
Posts: 876 - Karma: 10
so wut? does that change the fact that math sux donkey balls.



'WHAT THE WTF?!?!!?' -Armada420
Jan 27 2005 9:00PM
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DietCoke
Posts: 1317 - Karma: 7
Well, his velocity upon hitting the jump is root 392, or almost 20 m/s. i dont feel like solving the other part but that root 392 would help.

the answer to part b is he would go higher. more weight means more energy means more velocity upon hitting the jump. this velocity means more height.

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If hate were people, I'd be China.
Jan 27 2005 9:05PM
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dan.b
Posts: 866 - Karma: 10
your right it suck...
'Moi c'que j'propose c qu'on envoye chier l'monde, on leur paye une criss de traite'
Jan 27 2005 9:05PM
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dan.b
Posts: 866 - Karma: 10
so he would be 15.6244m? fuck that its impossible...
'Moi c'que j'propose c qu'on envoye chier l'monde, on leur paye une criss de traite'
Jan 27 2005 9:11PM
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DietCoke
Posts: 1317 - Karma: 7
are u kids remembering the 28 degree slope?

you have to do the (root 392) * sin 28 for the y component of the velocity


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If hate were people, I'd be China.
Jan 27 2005 9:14PM
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dan.b
Posts: 866 - Karma: 10
oups... i did cos(28)...
'Moi c'que j'propose c qu'on envoye chier l'monde, on leur paye une criss de traite'
Jan 27 2005 9:16PM
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dan.b
Posts: 866 - Karma: 10
than its 4.39878m in the air...
'Moi c'que j'propose c qu'on envoye chier l'monde, on leur paye une criss de traite'
Jan 27 2005 9:19PM
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dan.b
Posts: 866 - Karma: 10
but can you tell me how you found the speed...
'Moi c'que j'propose c qu'on envoye chier l'monde, on leur paye une criss de traite'
Jan 27 2005 9:23PM
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freeskier0808
Posts: 1748 - Karma: 16
i'd tell you if i could but i suck at math good luck
Jan 27 2005 9:31PM
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tride
Posts: 1038 - Karma: 26
It all depends on the type of skier;

Newschoolers would be leaving the jump at a sideways angle due to their sick carved take-off, and the pants might fall down during flight adding some parasitic drag.

Mogul skiers would pop super hard going the highest but all the twisters could create a vortex of air hindering their distance.

Racers would absorb the jump and stay on the snow, but with their bases and wax would probably be hitting the jump at 3 times the speed of the average jibber.


Jan 27 2005 9:34PM
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Adamskinick
Posts: 3353 - Karma: 126
actually B is THE SAME, the weight wouldnt matter on the back, sorry to inform u of this. i cant explain why, but that's the answer


Turtle: Cmon guys get dates, it'll be like Prom! Eric: So I guess that means you won't have a date
Turtle: Fuck you guys, I told you 10,000 fucking times, she had food poisoning!-Entourage HBO
Jan 27 2005 9:55PM
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LostCarKeys
Posts: 2553 - Karma: 20
Web assigns are so gay...





Live To Ski...
Ski To Live...
Jan 27 2005 9:55PM
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Adamskinick
Posts: 3353 - Karma: 126
dude they blow. but its 15% of my midterm exam grade, so its sorta easy points once u find a friend who knows this shit. i have until sunday morning to finish so i should be good
Turtle: Cmon guys get dates, it'll be like Prom! Eric: So I guess that means you won't have a date
Turtle: Fuck you guys, I told you 10,000 fucking times, she had food poisoning!-Entourage HBO
Jan 27 2005 9:59PM
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DietCoke
Posts: 1317 - Karma: 7
duudddeeee i was wrong. adamskinik is right.

potential energy = mgh and kinetic energy = .5mv^2

Since its all PE at the top and all KE at the bottom PE=KE. so mgh=.5mv^2

the masses cancel, so no it doesnt matter. easy grade

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If hate were people, I'd be China.
Jan 27 2005 10:04PM
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Adamskinick
Posts: 3353 - Karma: 126
thanks, i think ur right bro let me check it
Turtle: Cmon guys get dates, it'll be like Prom! Eric: So I guess that means you won't have a date
Turtle: Fuck you guys, I told you 10,000 fucking times, she had food poisoning!-Entourage HBO
Jan 27 2005 10:09PM
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amlowenstein
Posts: 1351 - Karma: 10
i wish we had done problems like that in physics
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603 STREETWEAR: february 2005
Jan 27 2005 10:10PM
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sherLocke
Posts: 4701 - Karma: 8
yeah because although he gains extra speed from going down the hill with the backpack. when he goes up the jump the backpack weighs him down more so he will leave the jump with the same velocity. word.


'damn son landing switch in pow is like...eating jello with a fork...'
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Jan 27 2005 10:13PM
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Adamskinick
Posts: 3353 - Karma: 126
true, but i still need to find out A that part is throwin me off. i mean i got 19.53 but i dont want to check it now, cause if i get it wrong i can never try it again, and lose the points. 20m is like 65 feet, pretty high up but i guess thats sounds right? the jump is around that height but it doesnt feel right, its cool though being a skier, i can relate well to this problem but i want the answer
Turtle: Cmon guys get dates, it'll be like Prom! Eric: So I guess that means you won't have a date
Turtle: Fuck you guys, I told you 10,000 fucking times, she had food poisoning!-Entourage HBO
Jan 27 2005 10:16PM
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sim
Posts: 1399 - Karma: -6
Dude, he will go 4.4084 m high. I'm sure of this. I did it with Energy and Projectile motion- with a derivative (I'm not sure if you learned that stuff yet.) I can explain it to you if you wish. If you think about it your answer- 19 something has to be wrong, because it would mean that he is going as high as he started. Meaning he left the jump at almost 90 degrees.



signatures are for pussies
Jan 27 2005 10:41PM
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3ski6guy0
Posts: 9201 - Karma: 132
i hate physics!! AHH!!
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Jan 27 2005 10:52PM
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mintcrue
Posts: 1593 - Karma: 25
Part A is 13.2 m at maximum height
Part B the weight would not effect the height because it cancels out

Strike 3
Jan 27 2005 10:59PM
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mintcrue
Posts: 1593 - Karma: 25
just use kinematic eqns to get initial vilocity and then u can use projectile motion easy steez from there

Strike 3
Jan 27 2005 11:01PM
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Adamskinick
Posts: 3353 - Karma: 126
13.2 or 4.4 u both make good points! i think 4.4 sounds more reasonable but then again he he have a huge in-run of over 60 feet goin fairly fast?
Turtle: Cmon guys get dates, it'll be like Prom! Eric: So I guess that means you won't have a date
Turtle: Fuck you guys, I told you 10,000 fucking times, she had food poisoning!-Entourage HBO
Jan 27 2005 11:21PM
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mintcrue
Posts: 1593 - Karma: 25
yeah however fast 19.8 m/s is I guess. I don't fuck around when it comes to physics... it's 13.2 dude remeber there is no friction or air resistance too.

Strike 3
Jan 27 2005 11:30PM
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Jibmaster_J
Posts: 491 - Karma: 8
sorry sherlocke, your wrong. he will still go the same height with the backpack, but its because acceleration due to gravity is constant. no matter how much mass something has, it will fall at the same rate of speed on earth.
Jan 27 2005 11:48PM
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johnnypsunami
Posts: 5024 - Karma: 221
ahaha 'Why dont they have the fool doing a corked 7 or something that would really heat the problem up'

ahaha awesome...

write this as your answer

'If the skier has no ski's, then this problem makes no sense.'









Drop Cliffs not Bombs
Jan 27 2005 11:51PM
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Triple_Strum
Posts: 6382 - Karma: 946
I will be a physics teacher in a little over a year and a half from now :) Give me $50 and I will write it all out and scan it to you :)


I dream of winter.
Jan 27 2005 11:54PM
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mintcrue
Posts: 1593 - Karma: 25
that is what I said isn't it?

Strike 3
Jan 27 2005 11:54PM
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Reaps
Posts: 590 - Karma: 24
alright i worked through it quickly... might be some mistakes,, but heres what i got.

mgh = mv^2
65*9.81*20 = 65* v^2
196.2 = v^2
therefore v = 14 m/s ...

v in the Y-direction is 14*sin 28 = 6.57 m/s up

When the skiier reaches it's greatest elevation, we have Vy = 0 ;

V^2 = Voy^2 + 2a(y - yo)
so 0 = (6.57*6.57) + (2 * -9.81)(y - 0)
-43.1649 = - 19.62 (y)
therefore Y-max = 2.2 m
Jan 27 2005 11:57PM
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Triple_Strum
Posts: 6382 - Karma: 946
^dang, for free.


I dream of winter.
Jan 27 2005 11:59PM
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J.D.
Posts: 21362 - Karma: 5,142
^Mintcrue: yes, you were right. But thread maker guy, you should pay T-strum anyways, just so you can say you had a physics teacher help you cheat on your homework.

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Jan 28 2005 12:03AM
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sim
Posts: 1399 - Karma: -6
No no no silly. It is 4.408. Let us think about this. If say the angle was at 45 degrees and remembering there is no friction, the max height would be 10. Do you see this? If not stop here and quit physics, or just try harder. Now 28 degrees is approximately half of that, meaning you are looking at an answer around 5, but also remembering downward accel.
As already said, I did this question two ways, it didnt take that long and I can show you:

0.5mv^2=mgh I'm skipping the step of find the velocity at the jump lip.
so masses are cancelled.

0.5(sin28*19.81)^2=9.81*h

solve for h = 4.408

OR

h= h_0 +v_0*t -0.5 a t^2
h_0= 0

so

h= (sin28*19.81) *t - 0.5* 9.81*t^2

take the derivative and set to zero to find max h.
dh/dt=0= 9.30 -9.81t
solve for t from

-9.30= -9.81t
t=0.948

plug this value in to the original h equation and get 4.408 m

Im 99.5% sure this is right. If you can prove otherwise, go for it, and I'll finally realize that I deserved that C- in Engg349 (Mechanics)


signatures are for pussies
Jan 28 2005 12:14AM
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sim
Posts: 1399 - Karma: -6
Oh and reaps, you forgot your 1/2 factor.


signatures are for pussies
Jan 28 2005 12:19AM
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edmonton_skier
Posts: 3210 - Karma: 110
the new steez will be wearing pack packs so that u can go higher
Y-vez
Jan 28 2005 12:28AM
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Reaps
Posts: 590 - Karma: 24
oh yeah my half factor i forgot would have brought it to 4.4m,, koo
Jan 28 2005 12:28AM
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Nihiriju
Posts: 2061 - Karma: 27
well this shows that a lot of skiers don't know thier physics...ahh i use to liek physics alot, i had the bets teacher, but then i went to college....and now i hate with the passion of a thousand firey suns! ahahahh
ARTINGE-------if someone knocks on your door and askes to see your slong because there is a crazed slong moneky paintintg, don't show it to him, it is just a Scan, he really only wnats to see your stuff.
Jan 28 2005 12:52AM
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mintcrue
Posts: 1593 - Karma: 25
i did the second way and got diff. i musta made a math error somewhere

Strike 3
Jan 28 2005 12:58AM
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DrGonzo729
Posts: 1312 - Karma: 10
Fucking holy shit, bunch of freestyle skiers doin physics on the goddamn internet, now if all the poeple who say pot heads are retards, and shit like that, just stereotyping people, they should come and read this shit.
Jan 28 2005 1:04AM
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gypsy
Posts: 760 - Karma: 12
wow! this is the most intelligent thing i've seen on ns! keep up the good work; skier intellectuals turns out to be a paradox! i would love to join in but unfortunately this is way above me. i am indeed impressed!
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Jan 28 2005 1:08AM
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thecoyote
Posts: 1937 - Karma: 14
if you know physics that question is just a matter of plugging in numbers to a formula..ridiculously easy.
Jan 28 2005 6:18AM
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Lebbo
Posts: 1258 - Karma: 6
Easy question except I been at Uni too long and forgotten everything I learnt in physics at school.

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Timo (Fireside Lodge pimp) 'You just close your eyes'

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Jan 28 2005 7:52AM
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powderdream
Posts: 1112 - Karma: 12
.......i hate math .........
Jan 28 2005 9:41AM
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