Front wheel powers the back wheels and so if power at the back wheel can only be smaller than power on the front wheel then vehicle can not advance from left to right.
Why not?
Power does not have a direction, so whether left to right, or right to left is not relevant. If the vehicle can move, it can move in any direction we want: left, right, or sideways. It only depends on the gearing. There are no physical constraints that prevent this.
Of course there is a direction as the generator wheels in order to produce the power will need to oppose the moving paper direction so whatever you extract from there you can call that breaking power.
So if you have 10W of breaking power you will need a motor on the other wheels (back wheels) that also receives 10W just for vehicle to remain stationary(ideal vehicle in real world you will need more power on the back wheels to also cover the friction losses).
So in the ideal case with 10W generated and 10W put in to motor wheels the generator wheels will push the vehicle form right to left while the motor wheels will push the vehicle in the opposite direction left to right and since the powers are equal the vehicle will just not move in any direction.
Not sure if you ever played with a generator spinning it by hand then short the wires or just connect a load to feel the difference in the amount of power you need to apply in order to maintain the same rotational speed.
At some point I think I posted a photo of a scam "free energy" where they show a motor connected trough a belt to a generator.
If you think about that say you supply the motor with power and it is connected to generator trough a belt but motor will need just say 2W to cover the friction losses and nothing more. Now if you try to take 10W from the generator you can no longer just provide 2W to the motor as then you will not be able to get the 10W from the generator but you will need to provide the motor with those 2W for friction that you provided before and maybe another 12W so a total of 14W to get the 10W from the generator.
You can never get more power from the generator than you put in the motor if there is no energy storage device.
This wheel vehicle and the motor generator scam are basically the same sort of problem. Most people seem to be OK calling that motor generator a scam but this wheel cart is the exact same problem.
People seems not to get the generator part as I hear many times in my business people saying things like while not charge my RV battery while I drive as there is power available at the alternator that is free to use since I still need to drive anyway.
They have a hard time understanding that taking 1kWh from the alternator and putting it in the battery will cost them an extra liter of gasoline so about $1/kWh or about 50x more expensive than getting that 1kWh from a solar panel.
So there is no free energy available at alternator since as soon as you take power out of alternator say 1kW then you add an extra 2kW load to the engine (alternators are typically just 50% efficient so the other 1kW is just heat in the alternator).
A liter of gasoline contains about 9kWh of energy if you burn it but since engine is typically just around 20% efficient you can see how 1 liter is needed for 1kWh took out from alternator.
Same thing happens when you use the car air conditioner to cool the car the fuel consumption will increase.
Not sure why I made such a long comment as I'm sure nobody reads my long comments.