# How Fast do I need to go to make my landing?

1. Dec 1, 2008

### EthanPipping

Now I'm not the smartest person in the world...just a snowboarder trying to get some help...so here is the information i have...My ramp is 10ft tall and is at a 35degree angle...my landing is 32feet away...my totaly weight is 160 pounds...so how fast in miles per hour do I need to be going at the launch point to land properly at the end???

also I would like to have a simpler way to find this out on my own...I would like basic equations...I dont care if its the long way around I just need simple steps

if someone could write the steps out for me it would help me very much...as well as keep me from getting hurt

2. Dec 1, 2008

### arunbg

How much of projectile motion do you already know? Are you familiar with the equations of motion?
Or do you simply need a formula to plug values in for similar scenarios, and are not interested in understanding the principles from which it was obtained.

3. Dec 1, 2008

### EthanPipping

also my landing in 4 feet tall by 10 feet long that would make the it at 20 degrees

4. Dec 1, 2008

### EthanPipping

what do you mean by projectile motion...I expect the speed to be somewhere around 45Mph...and I am NOT familiar with the equations of motion...I'm just out of high school

5. Dec 1, 2008

### arunbg

I am not getting a clear picture of the setup. Specifically what do you mean by 20 degrees (what makes the angle)?
Projectile motion is the term given to motion or trajectory of objects in a gravitational field.
You can learn the basics from any introductory physics textbook or just google it.

Oh and welcome to Physicsforums :)

6. Dec 1, 2008

### EthanPipping

let me explain...I am going up the ramp at X mph I leave the ramp at a 35 degree angle UP...and I land 32 feet away now whats X?

the other information I though that might need to go into figuring this out was the hight of take off and landing as well as my weight

7. Dec 1, 2008

### arunbg

Your weight is not required. A basic calculation gives me 18.76 miles/hour. This is of course not considering any of the other factors like friction, drag, orientation of body etc.

8. Dec 1, 2008

### Gnosis

EthanPipping, while your body weight isn’t required for the calculations of your intend trajectory, you WILL need to send a dummy load down using your exact weight for several test runs to make certain the calculations, as well as your ramp construction are all as they should be. Don't make the jump based solely upon calculations.

Let’s double-check your intended construction and correct me if I’m incorrect.

1. Your launch ramp will be 10 feet high and angled 35 degrees from horizontal.

2. Measured from the top of the launch ramp to the top of the landing ramp, there will be a distance of 32 feet as measured horizontally although, your landing ramp will only be 4 feet tall therefore, 6 feet lower than the height of your launch ramp.

3. Your landing ramp declines at an angle of 20 degrees and is approximately 10 feet long.

Naturally, you need the launch velocity (x), but where are you getting the launch velocity from? We’ll need to know the hill you’ll likely be coming down, its angle, and height.

Also, why have you selected a 20 degree angle for the landing ramp?

9. Dec 2, 2008

### Mentallic

Well I assume you don't want to land right on the edge your landing ramp. I calculated that if you are to land in the middle of your landing ramp (I'm not exactly sure how snowboarders like to do it) you will need to add on 3 miles/hour onto arunbg's result.

10. Dec 2, 2008

### rcgldr

Was that 18.76 mph exit speed at the top of the ramp or entry speed at the bottom of the ramp? Plus you'd need a little extra entry speed to compensate for friction losses and aerodynamic drag. Lastly, how do you acheive an accurate speed with a snowboard (unless you're being towed by a snowmobile with a speedometer)? Sounds risky. Ski jumpers use a landing hill, not a ramp. Motorcycle jumpers use landing ramps and crash quite often.

11. Dec 2, 2008

### Nick89

I think everyone is forgetting that gravity is not projected straight downwards if you are using the angles provided by the OP.

Here is a picture to make this clear:

The first pic (a) illustrates what I think you are using to calculate the speed:
And the second pic (b) is how the ramp (most probably) looks in real life!

This will cause a very significant reduction in the required speed. In my own snowboarding experience I have even noticed ramps where (for your frame of reference) the ramp slopes steeply upwards, but if you look at it from the 'horizontal' frame of reference it is actually not even going upwards, but only tends to horizontal.

12. Dec 2, 2008

### arunbg

My calculations were based on a setup like fig.a in Nick's post. I also assumed the landing strip was 10 feet below and 32 feet away. The slope of the hill can certainly make attaining required velocity easier.
My calculation was pertaining to the velocity of the boarder at the top of the launch strip.
And this is probably a very inaccurate result for real life scenarios, the exact velocity required depends on so many factors. Again attaining that exact velocity will be a challenge in itself. If you are able to get a velocity greater than required from a given starting height on the hill(referring to fig.a), you can reduce that start height accordingly.

13. Dec 3, 2008

### EthanPipping

here is the other information you requested...I will be being pulled by a snowmobile on a flat long driveway...my intentions are to jump Center road. (the road I live on...not that that matters but this should be pretty cool) also my ramp is 35 degrees at the launch point not the entire ramp...the first 14 feet of the ramp will be at a 20 degree angle and the last 6 feet will be at 35 degrees....also I chose a smaller landing so I wouldn’t have to go to fast to kill myself

14. Dec 3, 2008

### Gnosis

And the plot thickens. LOL

So, you are on flat ground and being pulled by a snowmobile up to launch velocity.

Realize the following:

If you continue to hold onto the towrope as you head up the launch ramp (that is, if you intend to do so), you will be accelerated considerably faster than your straight-line snowmobile provided linear velocity! This is due to the increasing height of the launch ramp consuming a continuously greater length of the towrope while the snowmobile continues per its steady linear velocity. This creates an acceleration much like a water skier experiences when the skier turns in a direction that’s more perpendicular to the boat’s direction of pull.

The 20 degree portion of your ramp will create the first of your accelerations and the 35 degree portion of the ramp will create an even greater rate of acceleration. If you decide to let go of the towrope prior to the incline angles of your ramp, the drag, wind, and double incline ramp factors further complicate your required launch velocity.

My Best Advise: I would “bag” this idea before it bags YOU.

15. Dec 3, 2008

### rcgldr

16. Dec 4, 2008