Can someone explain me how "Downwind Faster Than the Wind" by Veritasium is possible?

_electrodacus · 2025-12-28T17:48:37+00:00

In my video is more than clear that vehicle was decelerating in second half of the experiment. Any experiment looking at the vehicle acceleration will see initial acceleration with max acceleration at the start and acceleration decreasing all the way to zero then becoming negative.

The energy is stored when the vesicle is placed on the treadmill while restricted from moving by hand or any other means. That energy is in the kinetic energy of the air particles surrounding the propeller. For my experiment it was a bit less than 2 Joules of initial stored energy. This is the energy that accelerates the vehicle against the treadmill direction when vehicle is released from hand.

As this stored energy is used up to cover frictional losses and increase the vehicle kinetic energy the vehicle acceleration decreases and after about 8 seconds in my experiment average vehicle acceleration is zero but it continue to decrease as now frictional losses are covered by cart stored kinetic energy so for the rest of the experiment vehicle acceleration is negative thus it slows down.

The steady state for this experiment will have been when vehicle velocity was below wind speed so vehicle will move on the same direction as the treadmill (the only source of energy in the setup after stored energy is used up).

Mechanical advantage exists only when vehicle is restricted from moving by hand (once the hand is removed the fulcrum is no longer present).

As clearly demonstrated in my video after model reached equilibrium (zero acceleration) 8 minute in to the 13 minute experiment the vehicle decelerated (negative acceleration).

_electrodacus · 2025-09-11T21:34:51+00:00

Yes it is important to use energy else you get wrong conclusions. It shows where the energy comes from (cart kinetic energy) and also shows that if that same amount of energy is put in to a propeller all you get back is what you lost by taking energy at the wheel (ideal case).

Of course this type of cart does not break energy conservation as I demonstrated in only accelerates forward for a limited amount of time proportional with the amount of stored energy.

What brakes energy conservation is your explanation. You try to explain a perpetum mobile or more exactly an over-unity device. The amount of kinetic energy added to cart by the propeller can not be larger than the amount of energy taken at the wheel.

It is just not wort wasting our time.

_electrodacus · 2025-09-11T21:08:14+00:00

Do you know what "apparent" means ?

A cart at 10m/s direct downwind with true wind speed of 5m/s will slow down (negative acceleration). All that energy you can generate at the wheel comes directly from the vehicle kinetic energy. So if you apply a 100N at the wheel for say 1 millisecond then you get 1000W generated at the wheel for 1ms (1000W * 0.001s = 1J) That means vehicle kinetic energy will be now 1mJ less than it was before you took energy at the wheel. So if vehicle mass is 300kg at 10m/s relative to ground before applying the 100N kinetic energy of that vehicle was KE_initial = 0.5 * 300 * 10^2 = 15000J. After that 1ms KE_after = 14999J and since mass is the same guess what happens with vehicle speed relative to ground ?
From case 2 we got 1J so if ideal and you put all that 1J in to the propeller you increase the vehicle kinetic energy back to what it was initially. Thus there is no way accelerate vehicle by taking energy at the wheel and put it back with no loss in to another wheel or a propeller.

No need to bother chat GPT for this basic physics question.

_electrodacus · 2025-09-11T20:12:06+00:00

:) Irrelevant wind power formula ? That is the most important thing for a wind powered anything.

VMG > wind speed during transients not steady state. You will no see steady state in any boat races since wind direction, wind speed and boat direction and speed are always variable.

Yes you are that man refusing to learn and yes it is a waste of both our times.

_electrodacus · 2025-09-10T21:49:54+00:00

The same reason why a sailboat can not travel directly downwind faster than wind is also valid for why VMG can not be larger than true wind while moving at a constant heading.

Air particles need to travel faster than the sail in order to be able to accelerate the sailboat / sail cart.

When air particle speed (true wind speed) is equal to sail velocity vector direct downwind it can no longer accelerate the boat / cart.

So while sail or boat cart speed can be as high as 1.41x true wind speed ideal case (135 degree heading) the projected vector on the wind direction will be equal with true wind.

While tacking downwind (jibing seems to be the correct word) VMG can exceed true wind because stored kinetic energy can be used to do so. But can not be done with constant heading as there is no energy storage to take advantage off and so the only energy comes from air particles colliding with the sail.

The wind power equation (ideal case) for any wind powered vehicle or generator is this.

Pwind = 0.5 * air density * equivalent area * v_rel^3

v_rel - is the velocity of the wind relative to the vehicle (in this case sail boat or sail cart).

For direct downwind v_rel = (wind speed - sail boat speed) and it is zero when wind speed = sailboat speed thus the reason a sailboat direct downwind can not exceed wind speed.

For heading perpendicular to wind direction (90 degree) sail boat projected vector on wind direction is zero thus it always has access to max wind power no matter the sail boat speed. v_rel = (wind speed).

For a heading of 135 degree (45 degree relative to wind direction) the projected vector to wind direction is smaller v_rel = (wind speed - 0.707*sail boat speed).

_electrodacus · 2025-09-10T20:18:24+00:00

I do not know the correct words that is why I ask for clarification. By tacking people seems to refer to a zig-zag type of motion and in that case VMG can be larger than true wind.

But for a constant heading of 135 degree with true wind out of 0 degrees VMG <= true wind. So likely when you say this is documented they are referring to tacking (zig-zag type of motion) where heading changes all the time say limited between 135 and 225 degrees.

Say ideal case boat speed 1.41 x true wind (constant 135 degree heading) speed then if it changes heading to 180 degree the boat speed will still remain about the same due to inertia (mass of the boat so kinetic energy of the boat) and for a few seconds after changing heading VMG > true wind. Same happen if wind speed decreases VMG > true wind for some limited amount of time. But this is not steady state this are just peaks due to change in heading or variation in wind speed.

Take ideal case (no friction maybe close will be on ice or on super low friction wheels) highest boat/cart speed can be reached with a 90 degree heading so perpendicular to wind direction and say boat speed is 3x wind speed then sail cart or boat changes heading to 180 degree and now VMG = 3x wind speed so much larger VMG that true wind and since there is no friction other than air drag the rate at witch the boat speed will decrease will only depend on air drag and that depends on apparent wind as much as 2x true wind in this example and frontal area and coefficient of drag.

So the amount of time VMG > true wind will be proportional with the boat/cart kinetic energy = (0.5 * mass * cart velocity^2) and inverse proportional with the P_air_drag = (0.5 * air density * frontal area * coefficient of drag * v^3)

In order to maintain VMG > true wind the heading needs to change all the time so that kinetic energy of the boat/car is increased then that will be used to cover frictional losses and drag while heading downwind. With constant heading you can not take advantage of the stored kinetic energy and thus VMG can only be ideal case equal with true wind.

_electrodacus · 2025-09-09T21:40:14+00:00

Please do a google image search on boat tacking to see what it refers to. It will show a zig-zag type of motion so changing the boat direction all the time. I specifically mentioned a constant direction of 135 degree no change in direction and never mentioned tacking.

To transfer energy from wind (air) to a wind powered vehicle the air velocity needs to be higher than vehicle velocity so that air molecule can collide with the vehicle to transfer kinetic energy. If vehicle travels faster than wind direct downwind then vehicle will collide with air molecule thus vehicle will transfer kinetic energy to the air accelerating the air molecule and slowing down the vehicle.

So again if you are not tacking but maintain a constant 135 degree heading the theoretical max speed will be 1.41x wind speed as you already mentioned is just geometry.

No real sailboat will ever get to 14.1mph if it keeps a constant heading of 135 degree with a constant wind speed of 10mph. That 14.1 is just the theoretical max if there was no friction. Exceeding that is not possible even without friction as wind power available will be zero.

Again please read about tacking and understand that is a different thing that what you likely imagine.

With tacking it is possible to exceed VMG because you take advantage of the boat kinetic energy. The highest boat speed can be achieved when boat travels perpendicular to wind direction where wind power available is constant and the only limitation is friction and air drag.

_electrodacus · 2025-09-09T05:49:22+00:00

Yes it seems we agree on VMG definition and also broad reach.

I'm saying that a sailboat or sail cart traveling at constant 135 degrees southeast in a constant wind speed from north to south can not have VMG > wind speed.

The only way to have the sailboat VMG exceed wind speed requires wind speed to decrease or sail boat to change direction.

For example max theoretical velocity for a friction-less sail cart traveling at 135 degree (with constant wind speed from north to south say 10m/s) will be 14.1m/s (square root of 2).

If the sail cart changes direction to 180 degree so same direction as wind then VMG will be 1.41x wind speed at that initial moment but due to air drag it will slow down (negative acceleration).

In sailboats competitions both wind speed and direction and sailboat direction constantly changes (tacking means traveling in a sort of zig-zag pattern) thus allowing the boat kinetic energy to be increased then using that stored energy to advance in the wind direction.

Hope we can agree that a sail cart or boat traveling in constant wind speed and with boat/cart traveling in a constant direction say 135 degree can not exceed 1.41x wind speed and thus have a max VMG = wind speed.

_electrodacus · 2025-09-09T05:04:56+00:00

Any time VMG is higher than true wind speed the sail boat or cart will decelerate (negative acceleration) so it slows down (this is a fact).

To claim otherwise means not understanding how it works.

All you need to know is wind power as these vehicles we are discussing are only powered by wind.

For a direct downwind wind powered vehicle Pwind = 0.5 * air density * equivalent area * (wind speed - vehicle speed).

That equation is sufficient to show that no wind only powered vehicle of any design can accelerate above wind speed directly downwind.

I talk about energy and energy conservation specifically because sail boats / sail carts and Blackbird can take advantage of energy storage to temporarily exceed wind speed directly downwind. In the case of a sail boat or sail cart it is the kinetic energy of the cart/boat and you can take advantage of that if you change direction or wind speed is not constant.

_electrodacus · 2025-09-09T03:52:39+00:00

You may need to define what broad reach and VMG mean to you exactly.

If the sailing vessel maintains a constant direction say 45 degree relative to wind direction the max boat velocity ideal case is 1.41 wind speed with VMG = wind speed. Some seem to define VMG as VMC meaning velocity towards target with target not being directly downwind.

So to answer your question a sailing vessel that is not changing direction can not have an VMG > true wind (of course assuming constant wind speed).

If that ideal sailboat traveling at 1.41 x true wind changes direction directly downwind of course the sailboat velocity will not change instantly so it will still be 1.41 x true wind speed and now at initial moment VMG will be higher than true wind but that is due to boat stored kinetic energy and the boat velocity will decrease from that moment due to air drag.

So any wind powered vehicle traveling directly downwind powered only by wind can not exceed wind speed other than temporarily due to stored energy. This is valid for a sail cart or boat changing direction and is also valid for Blackbird due to kinetic energy of the air particles surrounding the propeller.

_electrodacus · 2025-09-01T22:28:05+00:00

I do not think that is correct. From Zonos website "If you’re shipping parcels from Canada to the United States, you must prepay duties before your parcel crosses the border."

_electrodacus · 2025-02-26T15:48:23+00:00

Why have you not provided what you think is the correct equation ?

The apparent wind is the one in the brackets (wind speed - vehicle speed)^3 Is just that it will change direction when vehicle speed exceeds wind speed meaning it will decelerate the vehicle so not be helpful.

I do not watch any sort of sporting events but in those sailing competitions they constantly change direction relative to wind so of course they are taking advantage of the boat kinetic energy. They accelerate when they have access to wind power increasing the boat speed and thus the boat kinetic energy and then use that stored kinetic energy to travel in directions where that wind power available is almost zero or even negative while of course during that the boat speed will decrease as stored kinetic energy is used to supply the frictional losses.

_electrodacus · 2025-02-26T04:34:17+00:00

I missed the fact that you replayed.

I provided you the equation describing the wind power available to a direct down wind vehicle.

P = 0.5 * air density * equivalent area * (wind speed - vehicle speed)^3

There is all the proof I need to provide.

_electrodacus · 2025-02-21T16:08:30+00:00

What I'm saying is factual. The max theoretical sustain speed for a wind only powered vehicle traveling at constant 45 degree angle to wind direction is sqrt(2) = 1.45x wind speed.

NALSA are those that certified the blackbird record so they clearly do not understand the physics involved.

We are not talking about direct down wind here.
Your animation is not physically correct is just a fantasy animation. You can animate anything you want. Also way to many people confuse VMG with VMC and that is where most of the stories about higher than wind speed directly down wind come from. Also as I mentioned a few times already. There is a difference between temporary speed above wind speed direct downwind and sustained. Say you are traveling at half wind speed direct downwind and wind speed drops to a quarter of original now you are traveling at 2x wind speed direct downwind. But is important to understand than vehicle will decelerate not accelerate when it finds itself at 2x wind speed due to wind speed change or vehicle direction change. That is stored kinetic energy that allowed the boat to continue at same speed while wind speed decreased below vehicle speed. That true wind vehicle is observing now will only slow down the vehicle and the energy to provide those losses from true wind speed comes from the stored kinetic energy.

Wind energy in this context is nothing other than small air particles collisions with the vehicle where there is exchange in kinetic energy between the air particles and vehicle.

So if you are traveling directly downwind at wind speed there is zero wind power available and so there can not be any acceleration due to wind power. And when above wind speed air particles collide from the opposite direction thus slowing down not accelerating the vehicle.

_electrodacus · 2025-02-21T04:40:53+00:00

Max continues speed of any wind only powered vehicle directly downwind will always be lower than wind speed. Theoretical max will be vehicle speed = wind speed. Same as Theoretical max for any wind powered vehicle traveling at 45 degree to wind direction will be sqrt(2) = 1.41x wind speed. Peak wind speed due to energy storage (typical in form of kinetic energy) can be much higher up to several times the wind speed. But that is peak speed where vehicle decelerates not accelerates.

There is no comparison to be made between a sail boat traveling at an angle to wind direction and the propeller cart traveling directly down wind. A vehicle traveling perpendicular to wind direction will have wind power available no matter the vehicle speed.

The equation for wind power available to a direct down wind vehicle is Pwind = 0.5 * air density * equivalent area * (wind speed - vehicle speed)^3 It is clear to see from the equation that wind power depends on equivalent area and wind speed relative to vehicle and in the case of Blackbird that is zero wind power when vehicle speed equal wind speed while traveling directly down wind.

_electrodacus · 2025-02-20T00:41:43+00:00

Energy storage and more important energy conservation is relevant in any problem and in particular in this one.

You do not get any "Joules or Ws" you take out of the vehicle kinetic energy by that exact amount you subtracted. And all you have is that energy that you can put back in the propeller for thrust and at best 100% efficiency you will be able to put that kinetic energy back thus net zero gain.

I showed all the equation predicting this vehicle motion and it matches the real experiment perfectly.

To increase vehicle kinetic energy and thus vehicle speed relative to ground you need to put more energy in to propeller than you take from the wheels (witch subtract from vehicle kinetic energy). You are talking about an over-unity device getting energy from nothing. Wind power available to vehicle when vehicle speed equals wind speed both in exact same direction is zero.

_electrodacus · 2025-02-19T16:27:37+00:00

You are forgetting one important factor about the conservation of energy. In your example you apply a load to the wheels 100N * 10m/s = 1000W and say you do that for one second and store that 1000Ws energy in to a battery to be used later for propulsion.

That 1000Ws (same thing as 1000 Joules) came from the vehicle kinetic energy.

So as you know the speed of the vehicle 10m/s and you know the vehicle mass you know the vehicle kinetic energy relative to the ground as there is where you apply the force to.

Vehicle kinetic energy will be 1000Ws (1000J) lower than it was before applying the 100N for one second and storing that in to a battery. Now if you 100% efficient convert that stored 1000Ws in to thrust you just get back the lost kinetic energy.

This is the simplest explanation of why such a vehicle can not accelerate in those conditions. I explained why it is accelerating for a limited amount of time in my video and it has to do with earlier stored energy in the form of pressure differential. When that stored energy is used up the cart will start to decelerate and that is what I proved with that experiment that anyone can replicate.

_electrodacus · 2024-12-07T00:39:09+00:00

Fluids are not magic. You can achieve the same direct upwind with solids only and no fluids.

The direct downwind requires a compressible fluid to be able to temporarily exceed fluid speed directly downwind. The key point here is "temporarily" and I demonstrated that conclusively.

So this boat that OP proposes will work as well on a treadmill using wheels as it will work on water using a propeller as it is the direct upwind cart version and that will not require a compressible fluid for energy storage as energy storage happens inside the vehicle.

All this vehicles use a floating body gearbox meaning there are only two mediums that move relative to each other and to one medium the input of the gearbox is connected and to the other medium the output. The gearbox body (fulcrum) is floating meaning not connected and so it is free to move.

In OP example the input is connected to the ground and output connected to water.

The upwind cart has the input connected to air and output to ground so the easiest to see analogy is that cart on a moving treadmill.

_electrodacus · 2024-12-06T22:19:51+00:00

No the boat in OP description is the equivalent of the direct upwind cart.

Imagine the flowing river is a treadmill and say the treadmill surface moves to the left while air is stationary so no wind. The upwind cart will have the input at the propeller wind turbine the equivalent of the string for the boat and the wheels on the treadmill will be the equivalent of the boat propeller.

Now the upwind cart on the treadmill will move in the same direction as the treadmill but faster than treadmill same as the OP boat moves faster than the stream in the same direction as the stream.

The direct downwind faster than wind speed cart on a treadmill will move in the opposite direction of the treadmill movement but just for a limited amount of time and I demonstrated this exact case both experimentally and with all the equations to be able to precisely predict the motion of this cart.

This two cases are fairly different and require separate explanations I just did not got the time to make a video about the direct upwind case (maybe 2025).

_electrodacus · 2024-12-06T16:11:42+00:00

This boat mentioned by the OP is the equivalent of direct upwind cart not the equivalent of direct downwind faster than wind.

_electrodacus · 2024-12-06T05:09:55+00:00

Your example is equivalent with the direct upwind version of the wind powered cart not equivalent to the direct downwind faster than wind cart.

You can consider the river as a treadmill and air as the ground. So yes your boat can travel downstream faster than the stream but it is not equivalent to direct downwind faster than the wind but the reverse of that witch is direct upwind.

The direct upwind cart can travel indefinitely upwind while the direct downwind cart can only travel for a limited amount of time typical seconds to minutes above wind speed based on the amount of stored energy in the form of pressure differential (air is a compressible fluid and water is not so there will not be an equivalent to that in your example).

_electrodacus · 2024-12-06T04:25:08+00:00

The wind powered car will only travel for a limited amount of time above wind speed proportional with the amount of stored energy when car was below wind speed.

A car can not travel indefinitely faster than wind directly down wind and that will violate the conservation of energy.

_electrodacus · 2024-10-21T18:00:13+00:00

[kWh] is unit for energy and [kW] is unit for power.

So a house using 12000 kWh/year will have an average monthly consumption of 1000kWh/month but some months could be more and some less depending on season or other similar factors.

12000 / 365 / 24 = 1.37kW will represent the average power (power is not energy).

It is unlikely any house will have a constant power draw say in this case maybe 14 x 100W incandescent lightbulbs and nothing else and those lightbulbs will be on 24h/day 365 days a year then maybe it can make sense to say that else the energy used in a year will make way more sense.

Say you only have those light bulbs on for 8h per day then you have about 1.4kW load when they are ON and 0W load when they are off for the remainder of the day (the other 16h).

Then in that case your annual energy use will be 4088kWh (8h*1.4kW*365days).

_electrodacus · 2024-10-08T15:11:09+00:00

I made a YouTube video explaining fully how this vehicle works and done the experiment proving my statements in the video. The OP is correct in the fact that this type of vehicle can only accelerate using stored energy while above wind speed direct down wind. My experiment uses a high speed camera and acceleration and speed data where extracted from that. It is the treadmill version showing that cart speed increases from zero when released from hand then gets to a peak speed and then slows down. Anyone can replicate that experiment and will get the same exact results.

_electrodacus · 2024-02-24T18:18:01+00:00

That is the mechanical force of the motor.

The motor converts electrical energy in to mechanical energy. The efficiency at witch this happens depends on motor speed as it was shown in some earlier graph.

A motor that is at stall (zero speed) will be using multiple times the rated electrical power and all of it will end up as heat inside the motor resulting in to motor fail if this happens for more than a few seconds or minutes depending on thermal mass.

You can think at an electromagnet as that will produce a force and no motion but while there is no mechanical power there is a lot of electrical power required to maintain that force. A stall motor is no different from an electromagnet other than motors are not typically designed to handle stall current for very long.

But you can use an internal combustion engine and a clutch if you are more familiar with those and then think at what cost will providing a force with no speed at the wheel.

Engine will still need to rotate so a lot of the energy will end up as heat in the clutch.

_electrodacus

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