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Posts: 2962

So I'm just doing this for fun, trying to calculate the pontential distance traveled of a jump (I'm think about this for a biking application but im sure it could be used for skiing as well). I havn't done physics since high school so I don't even know where to begin. I would think the following variables would apply: Gravity (-9.8m/s), velocity, mass of object (maybe?), angle of jump, air resistance (friction coefficient for air). I would think you would be able to figure it out from these. anyone know how to do it?

Posts: 1608

thats a pretty complex one. I could do it but i have no motivation at all to do any of that.haha

Im Ron Burgundy?

Posts: 1608

its basically the same as the problems where they ask how high the ball goes if thrown but you just factor in that it is not going vertical and that it has already been accelerated to its maximum velocity in the begging of the equation

Im Ron Burgundy?

Posts: 2962

ok cool. what if you are going off a jump with a gradual lip (i.e. constantly increasing angle)? Do you just go by the angle at which it leaves at or is there a further equation to factor in the curve?

Posts: 2416

the angle at which it leaves. also, for skiing, youd have to remember that the landing will be lower than the lip

-adrian

Posts: 2962

well there are a lot of variables but the landing might not be lower then the lip in relative terms. for example say you are comming down a 30 degree slope and hit a jump with a 30 deg lip. you are essentially dropping from a flat surface in absolute terms. so as long as you are landing on that same 30 deg slope then it would be the same as travelling from flat hitting a 30deg kicker and landing flat. So is it definate that mass of the objet and change in angle of the jump have no effect?

Posts: 2962

I think this is the right formula:

H =Vy T - 0.5g T^2

H =Vy T - 0.5g T^2

Posts: 2962

then Plug Time into x = Vx T

Posts: 1608

not necessarily

Im Ron Burgundy?

Posts: 1608

Im not sure about that one...im going to chicago right now but. im determined to figurte this out when i get home

Im Ron Burgundy?

Posts: 550

This my friends, requires a differential equation.

You have the resistance of the air which depends on the speed of the bike/skier... Air resistance is not like friction where you only need a normal force and coefficient. Air resistance relies on frontal area and velocity; which changes as you travel through the air continuously. You also have the inrun and the amount of kinetic energy burned off to friction between your wheels and the ground.

You have the resistance of the air which depends on the speed of the bike/skier... Air resistance is not like friction where you only need a normal force and coefficient. Air resistance relies on frontal area and velocity; which changes as you travel through the air continuously. You also have the inrun and the amount of kinetic energy burned off to friction between your wheels and the ground.

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-Brian

Proud member of the NS 6 foot posse

-Brian

Proud member of the NS 6 foot posse

Posts: 550

So now the question is... who besides me has taken university physics and a differential calculus class?

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-Brian

Proud member of the NS 6 foot posse

-Brian

Proud member of the NS 6 foot posse

Posts: 12074

thats mad easy to calculate tho

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-dan treadway

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Posts: 6219

if your going to take air resistance into account, then there's the fact that a peron.. on skis or a bike.. is probably moving while in the air.. ie: constantly changing face surface area. Then if the wind is blowing... yeah.. you might just wanna neglect air resistance for this one.

Posts: 1554

yeah i was about to suggest the same thing. or possibly find the maximum air resistance and just treat it as a constant because i figure its better to go a little bigger than hit the knuckle.

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Posts: 2962

ok so we are offically neglecting air resistance on this one. I think I got it to work. Basically I came up with a skiier/biker leaving a 20deg lip at 50kmh will travel 50ft anyone wanna check that?

Posts: 16725

well I will just say that a lip at 45 degreess will travel further, and theoreticly a 90 degree lip will luanch you just as far as a 10 degree lip.

And that is all that I think I know.

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I have a dream that one day all skis will have at least a 90mm wast.

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I have a dream that one day all skis will have at least a 90mm wast.

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Posts: 550

50kmh going 50ft in the air?

... units?!

... units?!

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-Brian

Proud member of the NS 6 foot posse

-Brian

Proud member of the NS 6 foot posse

Posts: 2962

I already did the conversions. I like working in feet for distance

Posts: 1865

gravity is actually -9/8m/s^2

the seconds are squared

the seconds are squared

fun

aka scratch23

aka scratch23

Posts: 2416

im in astrophys, but just starting second year, so no course devoted entirely to differential equations yet

-adrian

Posts: 2962

I've taken differential and integral calc. no physics though

Posts: 19021

ME ME ME! I sucked ass at physics though. C-. I got a B+ in Diff Eq though.

Posts: 2690

i got a 4 on the ap physics last year. mass is not needed but im sure i could figure that out.

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Posts: 1953

do you mean an 80 degree lip will launch you just as far as a 10 degree lip? a 90 degree lip will send you up, and right back down like a quaterpipe.

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Posts: 1264

a formula could be derived using dimensional analysis. take in all the factors, like you listed and put their units to powers of symbols and solve for the exponents creating an equation

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Posts: 1135

exactly i was gonna say fuck air resistance

Posts: 4071

this is an interesting thing to do for fun. i think you would be best off jsut treating it as a simple trajectory problem. air resistance and weight aren't going to be huge factors and would make it much more difficult. but if you want it really challenging, don't forget to consider wind, bagginess of clothing, width of skis, air density at different altitudes and relative humidity.

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Posts: 7419

Start with the horizontal distance you need to clear. Call it X.

The time the car will be in the air is

T = X / (V cos A)

A is the ramp angle from horizontal and V is the initial velocity.

One must also satisfy

V sin A = g (T/2)

because that it the vertical velocity component change in time (T/2)

Therefore

T = 2 V sin A/ g

Putting the two equaqtions together,

X / (V cos A) = 2 V sin A / g

X = 2 (V^2/g) sin A cos A = (V^2/g) sin 2A

You can use that equation to find combinations of V and A that work.

Note that sin 2A cannot exceed 1, and it has its greatest value when

A = 45 degrees. That will give you the lowest value of V needed for a given gap X.

The same equation comes into play when you are talking about the range and optimum launch angle of a thrown projectile.

A long jumper will also travel farthest if his/her takeoff angle is about 45 degrees.

(I found this on NS, don't know who posted it - hope it helps)

The time the car will be in the air is

T = X / (V cos A)

A is the ramp angle from horizontal and V is the initial velocity.

One must also satisfy

V sin A = g (T/2)

because that it the vertical velocity component change in time (T/2)

Therefore

T = 2 V sin A/ g

Putting the two equaqtions together,

X / (V cos A) = 2 V sin A / g

X = 2 (V^2/g) sin A cos A = (V^2/g) sin 2A

You can use that equation to find combinations of V and A that work.

Note that sin 2A cannot exceed 1, and it has its greatest value when

A = 45 degrees. That will give you the lowest value of V needed for a given gap X.

The same equation comes into play when you are talking about the range and optimum launch angle of a thrown projectile.

A long jumper will also travel farthest if his/her takeoff angle is about 45 degrees.

(I found this on NS, don't know who posted it - hope it helps)

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Posts: 1605

I'll help out in a while, I've just been working on this! I intend on putting it to use for both biking and skiing asap!

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Posts: 444

because gravity is measured by acceleration not velocity

Posts: 1470

solving a differential equation is not necessary, the velocity changes a small enough amount that you could neglect that. Air friction could be neglected all together and it would be a simple calculation.

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Posts: 1605

I have

Air resistance can be neglected. I was just looking through my old stuff, and I have a 2 page note on exactly how to do this, because I worked on it so I could put it into use when building. I'll upload it eventually for you. It's really well laid out and easy to follow, and all you'll have to do is plug-n-chug

Air resistance can be neglected. I was just looking through my old stuff, and I have a 2 page note on exactly how to do this, because I worked on it so I could put it into use when building. I'll upload it eventually for you. It's really well laid out and easy to follow, and all you'll have to do is plug-n-chug

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I dream of a better tomorrow... where chickens can cross roads and not have their motives questioned.

Pictures speak louder than words because some words are big and hard to understand.

- Crochet Cult

- Build a Jib Cult

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I dream of a better tomorrow... where chickens can cross roads and not have their motives questioned.

Pictures speak louder than words because some words are big and hard to understand.

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--> pm me for an invite

Posts: 498

2 words mad confusing

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Posts: 10775

def. dont have the time for this right now. but 2 things, mass does not matter, and get rid of air resistance **wayyy** to complicated unless you are willing to spend a lot of time with changing values etc. idk i didn't read the responses but hope that helps a little....

Posts: 1135

pics or it didnt happen

Posts: 873

the weird part is that i'm in grade 11 and had allready thought of all those variables. however, i dont know how to make the equation, but then again, ive never taked a physics or calculus class in my life.

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