Forget planes on conveyors...it's choppers in cars!
Discussion
Ok, so the awesome Aldi r/c helicopter has been bought. However, I was lying awake the other night thinking this one over. If I was to be hovering the helicopter in my car, and I drive off, what happens? Does the chopper stay static in the car or hit the back window? And what happens if I put the roof down?
Aaarrrghh!
Aaarrrghh!
Ah, but if you try and fly the chopper outside, it gets blown around by the wind. So it's hovering in a static piece of air. So if that air also moves forward with the car (accelerating very slowly) will the chopper come with it? Or, put it another way, if I'm driving down the motorway at a steady 70mph, with the chopper, rotors turning, in my hand, and I let it go, will it really hit a rear seat passenger in the face at 70mph?
Tricky eh?
Tricky eh?
The air does shift because it has mass so it does move like water in a tank would but with the roof down the chopper remains fairly stationary(subject to vortices created by your car moving off) but you don't. So roof up the chopper will move towards the window but not dramatically, roof off chopper disappears out the back of the car
Hard-Drive said:
Ok, so the awesome Aldi r/c helicopter has been bought. However, I was lying awake the other night thinking this one over. If I was to be hovering the helicopter in my car, and I drive off, what happens? Does the chopper stay static in the car or hit the back window? And what happens if I put the roof down?
Aaarrrghh!
Yes the chopper will stay static since there is no force acting upon it.Aaarrrghh!
When you accelerate in a car - you appear to be being forced back into the seat. In fact what is actually happening is that the seat is accelerating into your back and pushing you along with the car.
Since there is no "seat" force acting on the helicopter - it would stay where it was until it met such a force (i.e. the back window).
Of course the reverse also applies - if you are already travelling at speed and launch the helicopter - it will continue to travel along with the car - and if you braked - the helicopter would fly towards the front window (just think what happens to shopping on the back seat when you brake heavily).
Having the roof open would make a difference. If the helicopter launches into the air stream travelling over the car - it would feel a decelerating force due to wind resistance. Unless you counter this force with an opposing force inducing forward motion in the helicopter - the helicopter would fall behind the car since the car is inducing forward motion due to its engine/tyres that is lacking in the helicopter.
Of course there is a slight complicating factor - especially if the helicopter is light. Watch this vid:
https://www.youtube.com/watch?v=y8mzDvpKzfY
Hard-Drive said:
Ah, but if you try and fly the chopper outside, it gets blown around by the wind. So it's hovering in a static piece of air. So if that air also moves forward with the car (accelerating very slowly) will the chopper come with it? Or, put it another way, if I'm driving down the motorway at a steady 70mph, with the chopper, rotors turning, in my hand, and I let it go, will it really hit a rear seat passenger in the face at 70mph?
Tricky eh?
No only acceleration or deceleration would cause movement in the car.Tricky eh?
scorp said:
Is that something to do with bouyancy and air getting pushed backwards ?
Must be. Surely as the helicopter is heavier than air (hence requiring power to keep it aloft) it would act with the air rather than like the helium balloon moving the other way to fill the gap left by the denser air moving back?The air in the car will move forward with the car which will exert a small force on the helicopter and move it forward slightly but not enough. The helicopter will hit the back windscreen. Viewed from a fixed reference point outside the car the helicopter would move very slightly before the rear window of the car caught up with it.
scorp said:
The inertia of the helicopter will cause it to slam into the back of the car, although that will depend on how quickly the car accelerates.
Exactly, imho. Inertia tries to keep a hovering helicopter stationary. A real helicopter would not suddenly find itself shooting off at 25mph if hit with a 25mph gust of wind.Gassing Station | Science! | Top of Page | What's New | My Stuff