The bigger issue is what percentage of the energy used to operate the systems is wasted? I guarantee the effort it takes to load and launch the lead balls, or to operate the pump on the 2nd car, would move the car much more effectively than the systems shown.

Think of the slanted trough as a single-bladed turbine. It doesn’t matter if the system is closed or not, the motor is impelling the water against the ‘turbine’ and it ought to be able to harness some of the energy. Horribly inefficiently, of course, but possible.

Second one does NOT move. There is no momentum transfer (the circulating
water can be considered as no more than an odd-shaped flywheel)

A. The downward momentum of the lead bslls will deliver angular force to move the vehicle forward. The original location of theballs is irrelevant. Movement will depend on veihicle weight vs. ball weight and drop height.

B. The water will transfer kinetic energy to the slide at initial impact. It will transfer reverse energy at the funnel, but this will be a smaller amount due to reduced kineitc energy resulting from initial impact. Pump pressure will ultimately determine movement or lack thereof based on same essential factors above.

2. The water car will not work. Again, this can be explained using conservation of momentum. The water in the system never leaves (for the sake of this argument, let’s say all water is retained and nothing splashes out). All the momentum of the water is canceled by the rest of the water system since it is moving in a circuit. The motor powering the water circuit will impart energy into the water system, but this energy is used only to accelerate the water, or keep it at a steady rate to overcome friction forces in the pipes. The motor is not imparting any energy to the road in any manner, and no mass is being ejected from the system. Therefore, laws of physics state that the car will not move.

The majority of the force created by the pumped water would be at the nozzle and push upward, opposite the expelled water. If the vehicle moved anywhere, it would go up in the air and that is not going to happen. The water would also have to be at such a high pressure that 1) most of it would rebound away in an intense but fine splatter or spray and 2) the recovery system returning the water to the pump (apparently gravity fed) would not be able to keep up with the volume of water.

some amount of water will be leaving the system, i’d claim. it might be only a super small amount, but some will. so there is some motive force, although presumably never enough to overcome the rolling friction of the tyres.

?

http://www.cfcl.com/rick/pix/watercar.jpg

1. Yes, the falling water imparts a forward push because it hits the ramp.

2. The fallen water now hits the basin while moving backward. The basin must impart a forward push to the water to direct it into the return line.

Result is that the forces cancel out, because all the water is retained.

As for the pump adding energy, we’re not talking about perpetual motion. What counts is the result of the forces.

Dang; it doesn’t even say what issue they were planning the answers to appear in . . . .

The water truck does not move. Though the falling water pushes the truck slightly forward, that energy is absorbed by the catch-basin moving the water toward the pump. The falling water kicked the basin forward, which was full of water already. So the basin’s expending energy moving the mass of the water forward toward the pump.

If the water were expelled overboard like the lead balls, it would work.

The second one also moves. As some of the impulse of the water gets transfered to the car.

I think the lead balls might give the vehicle a small push. They have potential energy stored in their height, and they are leaving the system. Would they not be sort of like expelling rocket fuel?