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# Help with a scientific explanation

Former Member
Posts: 1,876,324

**The Mix Honorary Guru**
Ok im doing some physics coursework (oh yeah!) and I need help on wording the scientific explanation on why a model helicopter will fall slower the bigger the wing span is.

I know how it works i just dunno how to word it? I'm not going to use what people say directly, i'll put it into my own words. Or could anyone give me some good webpages? I've looked but i cant find any.

Thanks

I know how it works i just dunno how to word it? I'm not going to use what people say directly, i'll put it into my own words. Or could anyone give me some good webpages? I've looked but i cant find any.

Thanks

0

## Comments

The Mix Honorary GuruThe Mix Honorary GuruThe Mix Honorary Gurubut i think your more on about air resistance.

The Mix Honorary Guruhttp://rabi.phys.virginia.edu/105/2002/ps7s.html

The Mix Honorary Guruhttp://www.adl.gatech.edu/classes/dci/aerodesn/dci03.htm

Cetripetal acceleration = velocity (squared)/radius

the radius in this case is the lenghth of the wingsspan

the longer the wingspan, the smaller the acceleration

the velocity of the plane is taken to be the same, ie its at terminal velocity

the plane falls in a circular motion so the force is directed to the centre and is downward and is opposed by friction, ie the drag.

speed also = distance/ time

you should be able to work it out from these equations.

hope it helps

The Mix Honorary Gurubut i might be wrong

The Mix Honorary GuruThe Mix Honorary Guruwell i didnt see you give an explanation so i think youre full of bollocks u twat

The Mix Honorary GuruThough all objects fall at the same rate if you ignore air resistance (i.e in a vacume) regardless of mass or size.

The Mix Honorary GuruThe Mix Honorary GuruAs bomberman says, in a vacuum all objects will fall at the same rate. The reason why a larger wingspan would slow the model down in reality is simply because of wind resistance.

An object accelerates when one force upon it is greater than the other. At first the force dragging the model down is greater than the force pushing upwards, which is the wind resistance. When the two forces are equal the model will fall at a constant speed unless one force increases (such as the force upwards when it hits the ground).

The wingspan of the model affects the magnitude of the force pushing upwards, for obvious reasons. If the wingspan is large, then the force upwards is larger, and so the downward acceleration will be cancelled out quicker. This means that the larger aircraft will reach terminal velocity sooner, and therefore this downward velocity will be slower. The smaller aircraft has a smaller upward force, so will accelerate for longer before reaching terminal velocity.

Remember two things: the upward force is not fixed, and increases exponentially as the downward velocity increases; terminal velocity is not a fixed number.

Given that speed = distance x time, it then follows that if something is travelling slower over the same distance, it will take longer.

The Mix Honorary GuruYou should, before you start, clarify your theory. You must state that it is assumed both aircraft have an equal mass.

First of all explain that acceleration is a result of the forces acting on an object being imbalanced. If the forces are balanced then no acceleration takes place.

Second of all, explain that the downward force (in Newtons) is equal to the mass of the aircraft (in kg). This is because the force acting on the aircraft is simply gravity, which has a value of 1.

Third of all, explain that the upward force is wind resistance to the aircraft, and that this wind resistance is exponentially linked to the downward velocity of the aircraft.

Fourthly, explain that the extent of the upward force is dependent on the area of the wingspan. You assume that the wings have a mass of 0kg.

Fifthly, explain that the aircraft stops accelerating when the upward and downward forces are balanced.

Sixthly, explain that the larger wingspan means that the upward force is greater. This means that the forces are balanced sooner, given that the downward force is a constant. This, consequently, means that the smaller wingspan will allow for more accleration before the forces become balanced.

Seventhly, state the relevant formulae for acceleration and for speed, mostly to show you know them.

Eightly, state that given s = d.t, if an object has a greater velocity then it will travel the distance quicker.

There are other things that you would need to assume, but these things are assumed without question at GCSE level. And, basically, I cba going into it any further, mostly because my A'Level mechanics is a bit rusty.

The Mix Honorary GuruI didn't give an explaination because the correct one has already been given by mel-h, I refuted your shite.

The Mix Honorary GuruMass has no bearing on gravitational (downward acceleration) force.

Skive's The LimitIn a vacuum gravitational acceleration is the same for evey object here on earth's, something like 9.8 m/s/s so mass doesn't matter in a vacuum or with two objects that have the same drag.

An object will continue to accelerate towards the ground until the force of drag equals gravity's pull on the object i.e it's mass.

Mass does have an effect.

Skive's The LimitThe Mix Honorary GuruSkive's The LimitSorry I meant weight.

The Mix Honorary Gurutried to help her, i didnt say i knew the answerand i did say that she needed to check what i posted.if you know better than me then tell her the answer but dont slag me off seeing as thought i was just being helpful and honest.

solve her question,dont critisise me i was trying to help.The Mix Honorary GuruNo you didn't.

You must be losing your memory. Maybe you should party less, its obviously getting to you.

Why not?

I won't, but only because it would be no fun if your best response would be "you twat".

Lies, tbh.

The Mix Honorary GuruDon't hijack the thread. You said "this explains it perfectly" you were corrected with no personal attack and then you started calling people a twat. Nobody slagged you off. Get over yourself.

The Mix Honorary GuruSkive's The LimitThe gravitational pull is stronger in larger masses that's why they're heavier, but gravitational acceleration is constant in a vacuum for all objects (9.8m/s/s).

The Mix Honorary GuruGravity is the same outside a vacuum too, but varies with altitude.

The Mix Honorary Gurui dont get the second point

The Mix Honorary GuruThe downward force (N) = weight (N)

Therefore the downward force is 100N, in this example.

I hope someone can confirm if that's right- as I said, my mechanical mathematics is a tad rusty, as I haven't used it for nearly five years.

The Mix Honorary GuruHense the equations F=ma, Force [N] = Mass [kg] X Acceleration [m/s^2]

The Mix Honorary Guruall that still looks like a foreign language to me - then again physics isn't my best subject