Why Does a Boomerang Return?

[arevolutionist]

What causes a boomerang return?

 

[Danger]

It's a combination of aerodynamic lift, gyroscopic action, and a couple of other factors. Here's a nice explanation.
http://science.howstuffworks.com/boomerang.htm"

 

[rcgldr]

Not only do boomerangs return, but some shapes will fly in a figure 8 pattern, if you don't catch it on the initial return, it will fly by and circle in the opposite direction and return again.

 

[giordano bruno]

Yes but what i wonder is whys that the boomerang precess since is a case of balanced gyroscope

 

[Doc Al]

Yes but what i wonder is whys that the boomerang precess since is a case of balanced gyroscope

Because there's a torque on it. The aerodynamic force exerted on each blade is not equal, since the blades move through the air with different speeds. (While one blade rotates forward, another rotates backward.)

 

[DaveC426913]

Not only do boomerangs return, but some shapes will fly in a figure 8 pattern, if you don't catch it on the initial return, it will fly by and circle in the opposite direction and return again.

I though it was actually a cloverleaf i.e. 4 lobes.

 

[Danger]

Yes but what i wonder is whys that the boomerang precess since is a case of balanced gyroscope

The point pretty much is that the thing isn't balanced. One arm is longer than the other, so the centre of rotation is offset from the radius of the bend.

 

[Doc Al]

But balanced, four-blade boomerangs work too! When I used to be in the entertainment business (teaching in grad school ), I would make simple boomerangs out of cardboard and wing them around the auditorium.

 

[Danger]

Well... yeah... but you're kinda weird.

 

[NateTG]

Ignoring gravity, it's a natural tendendcy of anything that's moving through a viscous fluid (air, or water, or whatever) to either move in a circle (or a straight line, which is , really, a degenerate circle.)

A boomerang is essentially a wing - something that generates a lot of acceleration while going through the air so that it curves more.

 

[DaveC426913]

The Wiki article covers the physics pretty nicely.

 

[giordano bruno]

The wiki doenst talk too much on the physics of it

Intuitivile you may consider than when it is spinned around its center of gravity there's more mass on one side of the boomerang than in the other but this is false by definition of center of gravity

On the other hand i had a boomerang which was regular not with wind shape and still worked

So my question is if precession only happens only on unbalance gyros how comes it appears in a boomerang that is a balanced one being the COG and axe in the same point

 

[Doc Al]

So my question is if precession only happens only on unbalance gyros how comes it appears in a boomerang that is a balanced one being the COG and axe in the same point

I answered that in post #5--there's a torque on the boomerang! (By "unbalanced" gyro I assume you mean a gyro with an unbalanced torque acting on it--that's what causes precession.)

 

[ZapperZ]

The wiki doenst talk too much on the physics of it

Intuitivile you may consider than when it is spinned around its center of gravity there's more mass on one side of the boomerang than in the other but this is false by definition of center of gravity

On the other hand i had a boomerang which was regular not with wind shape and still worked

So my question is if precession only happens only on unbalance gyros how comes it appears in a boomerang that is a balanced one being the COG and axe in the same point

You have WAY too many things relying on your faulty "intuition" here.

Please read the link given by Danger in this thread. Scroll ALL THE WAY DOWN to the bottom of the page where are is a series of very extensive "intiutive" explanation about the dynamics of a boomerang. If you want a quantitative explanation and derivation, then you either need to sit down and work out the physics of the system, or pick up physics papers/books, and then tell us where you got stuck.

http://pass.maths.org.uk/issue7/features/boomerangs/2pdf/index-gifd.html/op.pdf

Zz.

 

[giordano bruno]

The point pretty much is that the thing isn't balanced. One arm is longer than the other, so the centre of rotation is offset from the radius of the bend.

but that center of rotation will coincide with the center of mass

Any object spinned unless forced to do otherwise will have the center of rotation in the center of mass

Therefore the force of gravity, second force in the couple is exerted exactly on the spinning axe with which there's no arm for the couple

Then why does it precess?

A posible answer would be that the superior wing gets faster air than the bottom one but this doesn't work with a boomerang that has no wing shape like the one i just build of hard paper which works as well

 

[giordano bruno]

i think the reason why the boomerang precesses is the tendence of masses to spin on preferred axes

if you spin a hollow ball rimmed with plastiline on the shape of a boomerang and spin it on the short axe it will end up spinning on the long axe, just like a football there the second force for the couple

 

[jasc15]

The fact that it was designed without any real knowledge of aerodynamics, or mechanics is really quite amazing.