Why Can’t a Magnet-Propelled Truck Actually Work?

There is a long-circulating meme on the internet that asks if a magnet-propelled vehicle would work. You can find a version of it on the internet. A drawing of a pickup truck with a metal plate on the front. A crane arm is extended from the back of the truck over the cab to hold a strong magnet. The theory is that the magnets will attract the plate and pull the truck forward.

I drew this drawing.

You know this wouldn't work. If it did, we'd already be driving around in our fuel-free magnets. Why don't you? Is it possible to make one work?

It's time to get to it.

There is a fundamental nature of forces.

Force is used to describe interactions. The chair pushes up on you because of the contact force between your bottom and the seat. gravity pulls you down when you stand on the Earth A piece of iron can be pulled on by a Magnet. The force is caused by the interaction between the two.

All of the examples are between two objects. Without the chair, an interaction between a person and a chair wouldn't happen. It's also true for the Earth and a person.

If object A pushes on object B, object B pushes on object A in a different direction. Every force has an equal and opposite force.

Equal and opposite forces can be measured. Two carts are on a track. The force sensors are mounted on top of the carts.

When I pull them apart, what will happen? The right and left carts pull each other. The left cart has the same force as the right one. Since the rubber band has a low mass, we can pretend that it's a fundamental force, like gravity or a magnetic force.

The force sensors are reading what is happening.

The two sensors have the same strength thanks to the third law.

There is a force rule that needs to be considered for our hypothetical vehicle. The second law says that a net force on an object changes its speed. The law is expressed as an equation.

The total force is equal to the product of the object's mass and its speed. Don't worry, there is avector version of this too.

The object's speed is determined by the acceleration. The net force on an object must be zero. If an object is at rest, it has to rest. This is important for our vehicle.

The truck has magnets on it.

The first thing to do is to try out a real-world model. That's easy. I can use my low-friction carts with a type of magnet crane as a stand-in for a full size version. This is what I built.

The Lego-based crane is connected to the cart with tape by a large neodymium magnet. If you haven't used them before, they're powerful. The cart has a bar attached to it. The force between the iron and magnet is so strong that it can pinch your finger.

Will the force of the magnet on the iron bar move the whole thing?

It doesn't work The cart is not moving. I could have posted this as a movie, but a movie that doesn't move really isn't that enjoyable.

It doesn't work. There is a slightly different cart that does accelerate. This is something to check out.

The cart on the right is moving faster and faster as it moves to the left.

The forces on this cart are shown in a diagram. This is a free-body diagram.

There are only three force interactions involving the cart if we ignore thefriction. The cart pulls downward due to the Earth's interaction with it. The cart is sitting on the track. The two forces have the same strengths and weaknesses. One is between the track and the cart and the other is between the Earth and the cart.

The last force between the cart and the magnet is meaningless. When the net force pulls to the left, the cart moves from being at rest to moving quickly. It is a real-life magnetic vehicle.

The idea of a truck with magnets seems to work. We need a force diagram for the cart to understand why it doesn't work. I will make three different diagrams. There will be two for the cart, one for the crane, and one for the Magnet. I color code the forces for you.

The forces on the cart are the first thing we need to discuss. The force of the crane pushing on the cart is the only difference now that the magnets and crane are added. The cart's total force is zero.

The force of the magnet pulling on the cart is the same as the force of this one.

The force on the magnet is balanced by the upward pull of the crane. The crane is trying to keep it from hitting the cart.

The crane is finally here. The most important forces here are the forces from the cart and the magnet.

The objects have no net force. Zero net force will cause a zero acceleration. The three objects that start with zero will not move. They're not moving. It's not going to work.

It's difficult to understand why this won't work, because you can't see the attractive interaction between the cart and the magnet. It makes it seem like magic.

If I keep the crane attached to the cart but replace the magnets and iron with a rubber band, the cart will not work. The rubber band creates an attractive force similar to the interaction between the magnets and iron. The rubber band can show the interaction. You can check it out.

I don't think anyone would expect that to happen. The same thing as the magnet cart.

Wile E. Coyote comprehends the laws of physics.

Wile E. Coyote in the Road Runner series is always trying to find a new way to catch a bird. He usually gets things wrong but sometimes he is right. It's sort of correct.

He puts out some bird seed. Wile E. attached a magnet to himself so that he could catch the bird after eating it.

There is a video titled "6KDgDYdug6M"

It doesn't work because in the cartoon the magnet gets attracted to the train and Wile E crashes into it. The force produced by the magnetic interaction wouldn't be enough to overcome the wear and tear on the surface.

The main idea is based on reality. Did you know that the iron and magnet are attached to two different things? The important thing is that. There are forces in pairs. The magnet pulls on the road runner Since the force from the magnet is on the Road Runner, he is able to zoom off to his own destruction.

Things look too good to be true at times.