what do you think would happen

[BLOFLY 636]

If you were riding a bike like a KTM 900 and were traveling along a test run way at 120MPH and you were approaching a truck with a 120 foot long trailer that was actually a ramp, this trailer is on a 25 degree incline and the truck is traveling at 60MPH. would you
hit the ramp at 120 MPH and continue doing 120MPH on the ramp which is still travelling at 60MPH which would then be an actual speed of 180MPH then ride off the edge of the ramp and jump the truck landing on the road and ride off with the speed reducing back to 120MPH
Hit the ramp at 120MPH and bog the engine down making it neccessary to down shift to raise enough speed to clear the ramp?
or just hit the ramp and die!
just a question that I have always wondered about but never asked anybody! I don't want to try to see what happens but it would be cool to know if it would be possible to jump a truck travelling at 60MPH!
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[Retro-Man]

Thats a little like the car & apple question,

If travelling at 60mph and you throw an apple from the window ahead of you, have you just thrown the apple at a speed above 60 mph
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[RascalsCustar...]

...well, the apples already travelling at 60mph. If it's thrown while its already moving, it'll accelerate past 60mph, but rapidly decelerate as it's not being propelled by anything.

But as for the truck scenario...if you're already doing 120mph and pass over something doing 60mph...you'll still continue at whatever speed you were carrying, as 120mph is more than 60mph.

Before i found out i always wondered if, if you were to jump out of a plane hurtling towards the ground at 150mph and jumped out right at the last second...would you still die? the answer of course is yes, cause in actual fact you're travelling at 150mph too! SPLAT! - which is probably what'd happen if you tried landing that stunt...thats assuming the bike doesnt go walkabout as mount the moving truck.

[Mr.Everready]

Same as the lift senario.
Your in a lift which is free falling down the shaft. If you jumped the split second just before it hit the ground would you be ok ?
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[G]

I suspect that you would need to pull the clutch in the moment your rear wheel went onto the ramp. I'd also want some pretty grippy stuff on the ramp .
At this point the rear wheel would decelerate from 120mph to 60mph if there's enough grip. This may well cause the engine to bog down when you let the clutch out.

After that you should continue up the ramp at 60mph faster than the ramp, presuming you're compensating for the slope with the throttle.



I have always wondered about riding a bike into a van while the van's moving. The problem again would come from the wheels suddenly decelerating from 60mph to 0mph, or whatever.

For the front wheel, maybe a wheely onto the ramp, with the front brake pulled on hard mid wheely to stop the front wheel.
Then maybe accelerate hard, followed by clutch in and light brake pressure to encourage the rear wheel to stop as it moves onto the relatively unmoving surface.

[mchaggis]

[Frost]

The ramp is traveling at 60, your doing 120. so you would still jump the same distance as if the ramp wasnt moving, landing say 100 meters from the point at which you left the ramp.
But you would only travel half that distance from the truck as in the time it takes you to cover that 100 meters in mid air the truck will have coverd 50.

So you could jump an actual 100 meters, but only a relative 50.


As for the apple thing, i think its one of newtons laws of motion. Things travel at a constant speed provided there is nothing to stop them. The apple in your hand is doing 60mph, you throw it up and it continues to do 60 as all the air in the car is going at the same speed. Gravity then pulls it down agian. should the car accelorate whilst the apple is mid air it would move backwards. Similarly if you hit a wall it's likely to try to keep going at 60mph and splat on the windscreen.

The lift jump one would work as the impact would be:

the speed the limt is falling - The speed your accelorating up. this would turn a 60mph lift freefall into a 20-30mph impact which is going to save your legs and spine


What would happen if you invented a time machine, went back in time and killed your grandad?

[mchaggis]

[lilredmachine]

Depends what you believe about causality. Some believe that everything is set out and that nothing different can happen, meaning that even if time travel were possible, you couldn't change much and you would probably still exist. Others believe that you would disappear, unless you had taken other precautions yourself. (like impregnating your grandma yourself before hand)

Wouldn't you be semi weightless in a falling lift? like in a parobolic dive? difficult to jump like that.
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[G]

But if you disapear, then you are back to the paradox.
Personally I think the universe would cease to exist , as it does exist that proves that time travel is improbable .

[lilredmachine]

Higher would equal more distance to build up impact speed by way of gravity = not good.
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[G]

Jumping high (well faster) relative to the speed of the lift, if done at the right time, should mean that your impact speed is lowered, as you are just falling at a relatively slower speed.

[mchaggis]

[Gazdaman]

Luckily lifts can't just freefall. If there's no cable suspended from the top little things pop out the sides and wedge into gears in the wall.

I'm sure it's not foolproof but lifts freefalling is very unlikely.

And I agree with mchaggis' post earlier about the KTM and the ramp. If you notice when a plane touches down there's smoke from the wheels as some rubber vapourises as it's accelerated from 0-100mph in practically no time at all.

Gaz

[Sparks!]

You should watch a film called "Down" the most recent one, poor acting and stuff but it's very good about a lift in some building that has a mind of it's own.. then ending is a bit shite but it's a fun film to watch..
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[Mr.Everready]

[mchaggis]

Here's a question for you then. You weigh 80kg and are wearing a rocket pack which can provide a thrust force of 20kN. Assuming you have no air resistance, and you fall from a height of 1km, how far from the ground (in distance and or time) do you have to set off the rocket pack in order to come to a perfect standstill just as you touch the ground?

Newtonian physics at its best.

Alternatively, to make it easier, assume a drag coefficient of 0.3, air density of 1.225 and your area to be 2m^2.
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[BLOFLY 636]

yeah it would be strange to assume that the bike would instantly go to 180MPH from 120MPH in a split second from when the rear wheel hits that ramp any one want to be the first to try it? maybe we should start with a petrol powered radio control car and have it travel at it's top speed now in front of the car a person riding a bike will tow a ramp along the ground 50 meters behind the bike at a speed 5MPH slower than that of the radio car, when the car reaches the ramp lets see what happens? place your bets ladies and gentlemen!
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[Frost]

Sorry i don't see where 180mph is coming from?

Is the ramp traveling towards the bike?

As in bike doing 120mph heading north and ramp doing 60mph heading south?

Or are both traveling in the same direction but going at different speeds?

[BLOFLY 636]

yeah the truck is heading north at 60MPH and the bike is closing in heading north at 120MPH trying to ride straight up the ramp and jump over the truck
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[Doug]

From a theoretical point of view i'm sure someone said the right answer in there somewhere (didn't read the whole thread, to tired for phyics/maths/whatever) but in practice the front wheel should lock as soon as it hit the ramp as it would decelerate from absolute 120mph/relative 120mph to absoute 120mph (cause the font wheel is being pushed by the back wheel) / relative 60mph (cause now it's on the ramp which is doing 60mph) insantaneously so therefore I recon the answer is:

or just hit the ramp and die!

Although it's probably best to ignore me for the night. My brain is not exactly in peak condition.

[WildGoose]

awww blofly, thought were you gonna show us a vid of what would actually happen after all that...


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[mchaggis]

Yes, the one part which gets interesting is when the front wheel is on the ramp but the rear isn't. Mind you, I think that problem is equivalent to a bike hitting a stationary ramp at 60mph.

As an analogy to the original problem, think of walking along, then continuing to walk at the same pace up an escalator. Think how fast you go relative to the stationary things, despite just going at the same walking pace relative to the escalator.
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[Mik_RX125]

If you want to find out what would happen. Put your bike on a paddock stand. Go up most of the gears and rev the nuts off it. Then get some brave person to pull the stand away. The bike would probably flip/stall or both as the rear wheel comes into contact with the ground.

With the ramp, theoretically (Studying A level Physics) the front wheel would lock temporarily as it slows down. As the rear wheel touches the ramp, unless you pull the clutch in, there is still a load of power there making the bike flip or wheelie. The bike probably wouldn't stall as its momentum would keep the bike travelling at 120mph relative to the ground.

Mik
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