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An engineer tests a new generator by attaching it to a motor-powered cart. The generator operates such that the cart's batteries charge when the cart's wheels turn. Assume the following true observations.

• Starting from a location, the cart travels Y meters in Z seconds, where Y and Z are non-zero, non-negative numbers.


• The engineer may power the car using one single motor, which is remote controlled. No human beings are pushing the cart or otherwise applying a force to it.


• The motor's battery levels are higher after the Z seconds have passed. The readings are accurate.


• The engineer has not altered the laws of physics and is on planet Earth.

Has the engineer somehow successfully built a perpetual motion machine, or is there some other explanation?

Simple explanation:

The cart moves downhill, and the gravity force is sufficient not only to cancel the friction, but also charge the generator. This version complies with the laws of physics and all given observations.

Of course,

the force is applied to the cart, but it's applied by the Earth gravity, which is obviously not a human being (the observation says no human beings apply the force to the cart).

An engineer tests a new generator by attaching it to a motor-powered cart. The generator operates such that the cart's batteries charge when the cart's wheels turn.

This is just like the regular fossil-fuel powered cars.

Starting from a location, the cart travels Y meters in Z seconds, where Y and Z are non-zero, non-negative numbers.

Which means the cart moved some distance and generator supplied power to charge the batteries.

The engineer may power the car using one single motor, which is remote controlled. No human beings are pushing the cart or otherwise applying a force to it.

The cart may be run by the motor using gasoline (for example) and still be remote controlled. The related electronics may still be powered by the batteries in question.

The motor's battery levels are higher after the Z seconds have passed. The readings are accurate.

The enery supplied to the batteries was higher than what was consumed by the remote controlling related hardware in the car, even after accounting for any losses.

The engineer has not altered the laws of physics and is on planet Earth.

Yes, they didn't.

Has the engineer somehow successfully built a perpetual motion machine, or is there some other explanation?

Far from it. The above explanation should help.

This is easy, and all answers are already fine. I'll try to gather all the conditions that needed to be true in order for the perpetual motion machine to have been true.

Obviously, the "catch" (what makes the scenario impossible in the real world) is not energy losses not considered, but energy gains not considered. Since our system is an energy cycle, all components must be considered. Thus, the conditions are:

 1. The generator only receives kinetic energy produced by the wheels

 2. The batteries only receive electrical energy from the generator

 3. The motor only receives kinetic energy from the batteries and/or generator

 4. The wheels only receive kinetic energy from the motor

If all of these are true, then this is indeed perpetual motion. I guess all possible answers will be instances of one of the above being false, having an unaccountd-for energy source instead.

It could be a:

Gravity train which is a theoretical means of transportation intended to go between two points on the surface of a sphere, following a straight tunnel that goes directly from one point to the other through the interior of the sphere.

A probably very silly solution:

Nowhere does it say that the generator or the motor is powered by cart batteries. Engineer just attached a generator, that runs on regular fuel, a motor, that is powered by this generator, and batteries, that are charged by the wheels turning. Funny thing is that a similar system already exists. Only it gets powered by external electricity.

Since the cart is controlled remotely, I think there are some limitations:

• The remote controllable distance is bound to have a limit


• The source of the remote control signal must somehow be supplied power

Of course the motor can be set to be infinitely on if there is no need for controlling power or steering. In that case it would probably qualify as perpetual motion.

Has the engineer somehow successfully built a perpetual motion
machine, or is there some other explanation?

The engineer is cheating. He or she is broadcasting the power from the remote control.

Wireless power transfer (WPT), wireless power transmission, wireless
energy transmission (WET), or electromagnetic power transfer is the
transmission of electrical energy without wires as a physical link. In
a wireless power transmission system, a transmitter device, driven by
electric power from a power source, generates a time-varying
electromagnetic field, which transmits power across space to a
receiver device, which extracts power from the field and supplies it
to an electrical load.

https://en.wikipedia.org/wiki/Wireless_power_transfer