MythBusters Episode 77: Birds in a Truck
Air Date: April 18, 2007
A truck carrying birds will be lighter if the birds fly around than if the birds sit/stand.
busted
Adam and Jamie constructed a large box and placed it on top of scale and then filled it with captured pigeons. Then, the Mythbusters activated a special contraption that would force the pigeons to fly into the air, but they could not detect any discernible difference in the weight of the box. They then placed a model helicopter inside the box and had it hover above the ground, but this method also failed to produce any results. The Mythbusters theorized that the air being displaced by the birds’ wings and the helicopter rotors was pressing down the box, which is why there was no change in the overall weight.
A boat moving at 25 miles per hour can be split down the middle by hitting a channel marker.
busted
Through small scale tests, the build team noticed that whenever they tried to have their model boat hit the channel marker dead on, the boat would just glance off with minimal damage. Tory then tried having the boat turn into the marker at the last second, which produced more positive results. Moving on to full scale, the build team acquired a used boat and had it crash into a specially constructed channel marker. The boat struck the marker, but only suffered minimal damage rather than splitting. The build team then tried moving the boat at faster speeds, but still could not split the boat. Wanting the boat to be completely destroyed, the build team opted to drop it from a crane, effectively busting the myth in the process.
What if the trailor had mesh or screen like sides. Some of the downdraft caused by the birds would sneak out of the trailor therefore causing the trailor to weigh slightly less….just food for though…
June 25, 2007 at 3:02 PMThe Boat being split , was not correctly done since the one thing “WATER” was not involved in the experiment. Instead of the boat glancing off the marker the boat would have impacted due to the surrounding water not allowing the boat to glance off because water has greater density than air.
Thanks
June 25, 2007 at 8:41 PMI also believe that the boat bisection myth test was flawed. the other problem is the way they turned the boat. The mythbusters were turning the boat into the post at the last second. Anyone who has driven a boat at speed knows that when you turn a boat, the attitude (angle) of the boat changes, but it can take some time before the momentum of the boat actually turns, so in effect, if the boat was turning to the left, the post would hit on the right side of the bow.
June 26, 2007 at 6:59 AMI think it would be interesting to try a ballon device versus the helicopter holding the same weight.
July 5, 2007 at 9:40 AMI agree with JH. It is easy to see the difference if you try to move a paddle against air and then into water.
The experiment should be done with the reported speed into the water. Increasing speed into water will not help to acomplish the “desired result”.
Jorge
July 19, 2007 at 1:06 AMHow they can call the boat test busted is beyond me it missed a direct impact ???
August 13, 2007 at 5:34 AMit was just a glance at best. Try again this time in water.
Hi, Just got this episode in Oz. I agree with everyone else. The boat test needs to be done in water. It felt all wrong to watch. You couldn’t possibly get an accurate result on land. Especially with the boat on a trailer. Seperate wheels fixed on either side of the boat ( without any shaft or axel ) would have given a better result if it HAD to be done on land.
August 14, 2007 at 8:24 AMYou have used full sized remote controlled cars, why not try a remote boat? Could be fun.. hint hint..
JH is correct. Water is a condition that should not have been removed from the test.
August 15, 2007 at 10:58 PMI agree, water adds resistance and would prevent the boat from bouncing off.
August 15, 2007 at 11:09 PMI used to own a sailboat—there’s a great deal of resistence from the water–to a bow on or port/starborad quarter impact. Your test had a boat on a trailer, on wet pavement—-if anything less sideways resistance than even dry pavement—-This is a do-over—your Bust is Busted
August 15, 2007 at 11:14 PMFurther more the slower a boat is going the more of the boats haul is in the water, which in turn adds more resistance. Do it again.
August 15, 2007 at 11:18 PMThe “Birds in a Truck” myth that was prematurely “Busted” is flawed due to a lack of precision in the scale used in the test. The registered weight of the truck should change, but OPPOSITE to common sense, and only in FLUX as the birds either rise or fall.
Birds gain loft when the normal force of the air flow they generate downward is GREATER than their weight, thus pushing them up. Since scales measure this normal force, birds taking flight in a truck should therefore INCREASE the weight of the truck. Now imagine that birds in flight suddenly stop flapping in midair and fall – they should therefore become “weightless” in freefall (they generate no normal force) and the truck should weigh LIGHTER. If the birds are at rest on a perch or maintaining a constant elevation, there should be no net weight change.
Or, think about it in terms of gravitational potential energy. Recalling that forces (like weight) are a derivative of energy with respect to distance, as the birds rise up in the truck, the truck must sink down onto the scale according to Newton’s third law, which registers as MORE WEIGHT. This explains why the weight should change only when the vertical position of the birds changes, and equal and opposite to their direction of change!
The above comments will only be observed in the most ideal conditions (for example, it ignores lateral forces), however they agree with theory, and anyone with a knowledge of Newtonian physics will agree – the truck will actually get HEAVIER as the birds FLY UP!
The problem with the Mythbusters method is that the scale used in the test was not precise enough to detect such a minute change in weight (they themselves noticed “noisy” data). The truck rig they used must have weight at least 1000 lbs., and the total weight of birds was at most 1% of this. I imagine (but cannot confirm) that a difference of +/- 1% is difficult to detect on an industrial-sized scale used in this test. I recommend a much lighter rig and more birds before this myth can be confirmed or busted. Or, James’s balloon idea sounds good!
August 15, 2007 at 11:48 PMYes, I agree with (CIH). The test should be made in a wire cage like container. The higher the bird is above the bottom of the cage, the less effect its weight and downward thrust. Please re-test. GRG
August 17, 2007 at 6:31 PMI don’t know about the U.S., but in Canada if birds are being transported by truck, it is never in an open trailer. Birds are much more sensitive to air flow and drafts than any other animal that would be normally transported. No one is going to pay for a truckload of sick or dead birds. Common sense should prevail in any retest. The trailer must be a solid container.
August 22, 2007 at 12:06 PMto confirm Mike bair’s comment, try jumping on a scale see if you weigh more at the moment of the jump
August 22, 2007 at 10:35 PMThe birds tested weighed so little that their effect on the overall weight of a truck is hardly measureable.
And Dorothy, I live near numerous tyson chicken plans… not one of these trucks ever transports the thousands of birds per truckload in an enclosed contanier. They are wire cages on a flatbed. (Of course… what am I saying… chickens can’t fly unless you shoot them out of an air cannon)
August 28, 2007 at 3:40 PMWith regards to the boat test, I completely agree with the others concerning the issue of course deflection in air versus water. It does need to be repeated in the actual environment that the documented crash occurred in. The momentum of the water immediately trailing the boat and tidal movement should also be considered.
You guys need to toast another boat. I suggest spiriting away my annoying neighbour’s cruiser. I’m very sure he won’t mind…really.
September 2, 2007 at 7:11 PMI also feel the boat test may have been flawed. Was the thickness of the fibreglass on 1/10th scale as well?? Otherwise it would give a false test.
October 8, 2007 at 5:02 AMThe boat test is flawed. Firstly the water is a very crucial part of the myth as it applies grater resistance to the boat vearing off line like it did in their test. Keeping the boat on line means that the force has to somewhere else.
October 8, 2007 at 5:30 AMI agree with Matt, The boat test is flawed. When you drive a boat at speeds and you turn the boat it doesn’t steer like a normal vehicle. The boat will go at an angle but the momentum will force it not head in the direction of the bow for a second or more.
October 8, 2007 at 8:15 AMThe boat test is critically flawed in not doing the test in water but on land.There is much more resistance in water than on wheels for a boat and you tested on a wet surface?? get it right
October 9, 2007 at 4:41 AMI’m not convinced the water is essential to the experiment but I do agree with Josh – the biggest mistake was trying to turn the boat INTO the marker instead of AWAY from it. The momentum would carry the boat into the marker slightly side on.
October 19, 2007 at 8:54 PMI know if birds/helecopters lift in the trailer the wieght is the same, BUT, if the birds/helecopters leave the trailer will the wieght stay the same? If not, WHEN?
December 13, 2007 at 3:04 AMWell, CIH that could work
January 1, 2008 at 11:53 PMWhat would determine whether or not a boat will split in half is the “cutting edge” of the marker. I recently saw a video where a guy split a remote controlled full sized car in half. The trick was to use a sharp blade that was held in place by reinforced concrete and elaborate braces. The car hit the solid marker at over 100 MPH. A floating marker is not a good example.
January 17, 2008 at 12:26 PMPigeons in a truck.
February 4, 2008 at 4:29 PMAs Jamie and Adam said, even the top minds in the field argue about this one. One thing I’d like to rule out is this downward pressure of the wings. I don’t believe the wings would have enough constant downward pressure to equal the loss of their weight but a simple test could be done to rule it out. Make a rig, like a long tractor trailer sat upright so there is a good vertical drop. Sit this on the four sensitive scales. In the centre of the top of the trailer have a hook with a remote release and suspend a heavy weight from the hook, say a small wrecking ball. Container plus ball equals total weight. When the ball is released it will be still inside the container but not attached to the container. Is there a change in weight before the ball reaches the floor?
I hate not knowing things. I’d love the physics of this shown.
Keep Busting!
Lance
Regarding the boat test, they also missed the weight of the engines in an actual boat… that would also help drive the boat into the marker.
March 12, 2008 at 10:55 PMI was very disappointed with the boat bifurcation experiment for many of the reasons already mentioned. I don’t think there is any doubt that a real, much heavier boat moving through the water would crash quite differently. Just the fact that it takes so much more energy to get a boat going 25 MPH on water than land hints at that. And they got too locked on to the thought that the boat had to have a twist-turn motion right before impact. All that turning rig did was slow it down. They should have crashed with a straighter path but with the front of the boat already turned askew.
March 13, 2008 at 9:46 PMI believe there were a number of things wrong with the splitting boat experiment. Its likely that for something like this to happen, bad weather would have been a factor. Bad weather means big waves. Big waves can toss and turn boats pretty easily. The waves may explain the angle the boat impacted the channel marker at as well as adding force pushing the boat harder into the marker (bad weather also might explain why the captain didn’t see the marker and hit it). I also believe the weight of the motor, passengers, and fuel would’ve added mass/momentum. Lets not forget the motor would have been running and therefore supplying a constant force pushing from behind the boat. The Mythbuster’s land based test used a “break-away rope” which does not pull after it breaks. The only other factor I thought should’ve been included in the test would be the sea life growing on the channel marker. The rough surface of barnicles on the channel marker might have grabbed and ripped open the boat rather than smoothly glancing it away. I understand the cost and difficulty in setting the full scale test in water, but I don’t think a land based test that includes all the right factors would be cheap or easy either. Don’t lay this one to rest just yet. There were too many external forces left out of the experiment to call this one busted.
March 17, 2008 at 5:35 PMI’ve just seen this episode repeated on Discovery, I thought the boat experiment was quite flawed too for a number of reasons;
1) Air is less dense then water and the deflection force will be less in water especially given the tilting angle of the boat if it turned before the point of impact. But I suspect the impact in the picture was right on the centre of the bow.
2) The steering wheels of the towing rig didn’t appear to alter the course of the trailer, the wheels just went perpendicular to the direction of travel effectively causing understeer to the trailer.
3) As mentioned above the engine(s) will continue to drive the boat into the marker thus increasing the impact forces rather then just relying on payload and momentum.
I too would love to see a full size remote controlled boat…that’d be cool!
All in all though I have to say its a great show and really entertaining, keep up the great work guys!
June 23, 2008 at 1:35 PMmany arguaments as to why the pidgeons in the truck did not alter the weight when flying or sitting.
September 9, 2008 at 1:03 AMthe helicopter waS A DISASTER.
if jamies coclusions are correct, then all trees and vegetation would be flattened each time a 747 passed over the fence with its weight of 300 + tons.
remember the principal of flight, the winds shape causes a suction and sucks , lifts the plane, the same applies to helecopter rotors.
no down force at all.
try again.
Hey Guys
Question here is who wrote the episode about the boat vs marker, was he new? or is this a cheaper form of research by acting out some form of experiment and let the viewers do all the work so you can produce a high quality do over. Adam why do you get mad at us viewers when we write comments regarding the flaws, or are you mad because you did’nt think of the obvious. Jamie, of all people, the one who seems to be able to analize every angle, oops.
With that being said, there alot of great reasons in the replies above for you to attempt a do-over.
Keep in mind a little background into the model of boat left half cut by the marker would go along way, like construction of the boat for weight reasons ie plywood, dryrot or moisture content could add 15% to the weight. Not all boat manufactures use the same construction or methods.
Well its been said many times already, TIME FOR A DO-OVER.
Try straight on and forget the mechanics of what goes on in a turn, if it fails on land head on without the option of turning then why go any further.
Other than a crash into a fixed post at 65mph would be cool, and test your RC skills.
Thanks for reading if you get down the list this far
P.S. cant wait to hear from your writer!!!
September 17, 2008 at 1:30 PMWILL MYTHBUSTERS EVER DO A MYTH WHERE THE VIEWERS HAVE NOTHING BAD TO SAY ABOUT IT.
October 9, 2008 at 10:17 AMThe boat hitting an unlit green day marker, with the impact halfway splitting the hull, is not a myth.
TowBoatU.S. Baltimore, MD did the wreck removal of the vessel and we have pictures…
It’s not a bad comment about the show, just a real fact that all the “busted” myth’s are not myth’s at all.
Jerry Cardarelli
December 23, 2008 at 1:55 PMVice President
BoatU.S. Towing Services
http://www.BoatUS.com
Jerry,
The Mythbusters stated in the show that they *know* it really happened. That’s not the myth. The myth being tested was whether or not the boat split at 25 mph.
March 1, 2009 at 4:08 AMyou all miss the point accept for justin.
March 17, 2009 at 9:28 AMyes water is dencer than air BUT anny boat I have ever driven at 25 mph or above is at plaining speed. IE 75% of it is not even in the water.
The damage shown IS possible BUT NOT AT 25 mph.
25 KNOTS is substantally faster (boat spedos read KNOTS not mph the mythbusters are still smarter than the lot of you accept it.
I’m glad my posting got some attention. :-) Also… I did miss the part they admitted it was true. Sorry!
They should have done the test with a true to scale and composition fiberglass boat, the equivalent weight and torque of twin engines and at planing hull speed.
Maybe we should take them to the Naval Research Lab in Potomac, MD? :-)
May 9, 2009 at 10:24 PMOn the myth in which flying birds makes a truck lighter, I think the reason why the truck remained the same weight is because when the birds were flying, gravity was still pulling on the birds and weight is the amount of gravity pulling on something. So in my theory, when gravity was pulling on the birds, the same gravity was pulling on the truck just like as if the birds were sitting. If the birds were next to the truck, the gravity pulling on the birds would not pull on the truck at the same time.
June 19, 2009 at 11:40 AMThe downward force of the birds wings does increase pressure, but as Bernouli’s Principle will show you, the pressure above the bird’s wing is reduced by roughy the same amount. If you use a wire cage it would be the same as measuring fish in a water tank swimming versus laying on the bottom with water pouring out the tank through a hole and a hose above pouring water back in at the same rate. There is not a vaccuum above the bird’s wing but rather a low pressure which sucks in more air to return the total pressure to the same as before. The only difference is that air is compressible and liquid is not, but at the speed the bird’s wing’s are moving I think compressibility is a rather small factor.
June 23, 2009 at 12:30 AMI agree with the cynics of the boat crash test. How could the back-ups call that busted? Crash the boat in water to avoid the boat glancing off the pole.
June 25, 2009 at 3:08 AMAnd a comment to the other nathan. Many boats read in mph, and kph. Do a little research before posting.
June 25, 2009 at 3:09 AMThe entire episode was VERY disappointing.
It was IMMEDIATELY obvious the boat test was COMPLETELY flawed.
This was a real low point in the show for me.
Well that and how ‘commercial’ it has become.
The same footage is repeated about 5-6 times per episode, and I am starting to find the narrator’s voice REALLY annoying.
This show was SOOOO good before the bigwigs changed the format to milk every last cent out of an episode.
Having said that, I do like the show (used to love it), and am EXTREMELY impressed with the up-held lack of product placement.
One last thing, can someone please just buy Keri a fricken YO-YO so she can watch THAT go up and down instead of her weight! and for the love of gawd, someone pay a live human female to help Grant retire those cracked and sun-faded V-Plates before it’s too late for him!
June 27, 2009 at 4:56 PMAfter my previous comment, I realized I forgot to add that Kerri and Grant are both legends! I was only pulling the piss! Lol
Oh and Adam, I want you to do your Ozzy accent more!
It never fails to crack me up!
Adam is definitely one of the biggest legends the world has ever has the privilege of being entertained by!
Big ups to the A-star ;)
June 28, 2009 at 1:17 PMI seen that one the birds in the truck i predicted the truck will remain the same.
Becuz the birds sit/standing was measured, and lets say that each bird weighed 200 Newtons…and they need exactly(but not really accurate) 200 Newtons to keep em floaking around(they cant go any higher)
so there (for each of them)downward force is gonna be 200 Newtons (exactly same with the helicopter)
December 3, 2009 at 5:42 PMGrant: Your science teacher(s) failed you very badly.
This episode was very disappointing on all counts. Trying the boat bifurcation on anything but water is a moronic waste of time. Also, the manner and material of construction of the “myth” boat must be duplicated, else the whole test is meaningless.
Regarding the birds in the truck, all of the scales they used had far too coarse resolution to detect the tiny changes they were looking for. There were a lot of assumptions made, adding up to some very bad science. For example, they assumed that helicopters lift by blowing air downwards. They don’t. Helicopter rotors are airfoils, just like airplane wings. The lift is by bernoulli principle, not like a fan blowing down.
A good example was given above: Suspend a big heavy ball from the roof of a tall truck. Total weight = truck + ball. Let the ball drop. Total weight suddenly drops by weight of ball. Ball hits floor. Huge instantaneous weight increase, then total weight stabilizes at truck + ball. If ball hasn’t gone through floor.
Same principle for pigeons. Total weight = truck + pigeons. Slight increase in weight as pigeons take off, then weight = truck – pigeons. You would need a very sensitive scale to measure this.
March 8, 2010 at 5:41 AM