I know a there are a lot of replies already, but I feel like the best way to explain is it’s similar to trying to push a car while you’re in it.
Comment on Lifehack for naive schoolchildren
Rizoid@programming.dev 10 months ago
I’m a big stupid and can come one smart explain why this doesn’t work in reality?
Jerkface@lemmy.world 10 months ago
_danny@lemmy.world 10 months ago
I think this is the best answer. Just because magnetism is not visible doesn’t make it magic. The source of the forces doesn’t change where those forces go. A lot of these perpetual motion machines can be simplified to a situation that makes intuitive sense.
MystikIncarnate@lemmy.ca 10 months ago
Basically, as much as the magnet on the car is pushing it forward, the magnet on the stick is pulling it back and it doesn’t go anywhere.
Kase@lemmy.world 10 months ago
So, hypothetically, what if we replaced the magnet on the stick with a stronger magnet? (I’m sure this wouldn’t work, I just don’t know why it wouldn’t work lol)
cley_faye@lemmy.world 10 months ago
The same. The attraction from one magnet to the other is the same on each magnets. If one is stronger, the total attraction is higher, but still the same on both ends.
Jiggle_Physics@lemmy.world 10 months ago
JDubbleu@programming.dev 10 months ago
Every force has an equal and opposite reaction.
When you are holding the magnet in front of the car you are pulling the car along through the magnetic attraction between the magnets, and the car is pulling the magnet back towards itself with equal force. However, you can just pull the magnet away as the car gets closer. When you do so you are transferring the force the car is imparting on you into the ground you are standing on.
If you were to now get on top of the car and hold the magnet in front of it the magnet you are holding would be pulled towards the car, and the car towards it. However, since you are on top of the car, instead of the force the car is imparting on you going into the ground (allowing you to keep moving the magnet away from the car) it would go back into the car. This force going back into the car is identical to the force the magnet you are holding is imparting on the car. As such they cancel each other out and the car does not move.
If you repeat the above, but replace the magnet with a rope, it’s a lot more clear why it doesn’t work. You can’t pull on a rope while sitting on a car and expect the car to move. The magnetic force is the rope, and you pulling on the magnet is the same as pulling on the rope.
niktemadur@lemmy.world 10 months ago
One magnet does not pull on the other, both are pulling on each other.
Sallp@lemmy.world 10 months ago
It is both pushing and pulling at the same time.
match@pawb.social 10 months ago
It doesn’t work because, while the front magnet is pulling the car magnet forward, the car magnet is also pulling the front magnet backwards and the front magnet is also attached to the car, so it cancels out.
Rentlar@lemmy.ca 10 months ago
In simplest terms, the two magnets are trying to pull toward each other equally. But when you glue them on the board, that glue holds the magnets apart, and “pushes” them the same amount that the magnets “pull” towards each other, hence no movement.
There would only be a movement if one side was pulling more than the other. The hand is providing that imbalance at first which moved the car.
Annoyed_Crabby@monyet.cc 10 months ago
Magnet want to pull and stick to each other of the different pole. When it glued to the car, the one on the cardboard will want to move toward the car and the one on the front hood will want to move toward the cardboard. The force cancel each other out so no movement will happen.
Johanno@lemmynsfw.com 10 months ago
Ok when not glued: both magnets get pulled to each other. The hand has to use some force in order to stay in place, so the car moves.
When glued: both magnets still get pulled to each other, but now the force is cancelled out since the force that would pull it forward also has to be used to hold the other in place.
Slow@lemmy.today 10 months ago
I think it’s the same as trying to give a sailboat acceleration by trying to blow the sails while standing on deck.
lemmefixdat4u@lemmy.world 10 months ago
Not quite the same as the two magnets. If you have a big fan and a square sail, you’re moving air, which has mass and is not attached to the boat. That alone will cause a force that moves the boat backwards. The moving air that hits the sail will not fully cancel that force due to frictional losses and air spillage from the edges.
Racing yachts are a different story. They have rigid sails that are shaped like airfoils. Blowing across an airfoil causes lift. So a big fan blowing perpendicular to the axis of the boat across such a sail would move the boat forward. But it’s much more efficient for the fan to blow backwards without the sail, hence airboats and hovercraft.
JohnSwanFromTheLough@lemmy.world 10 months ago
If you could scale the strength of blowing all the way up this would actually work though no?
gerryflap@feddit.nl 10 months ago
If you’d blow with a leaf blower or something to the front of the boat, the boat might actually go backwards of there’s enough force. The leaf blower is basically pushing the air forwards, therefore it’s also pushing itself backwards. Some go this will probably be cancelled by blowing against the sail, but some air will also pass around it.
hawgietonight@lemmy.world 10 months ago
In this situation the magnets act much like a spring, so imagine changing the magnets on the stick and the car for a simple spring. That is much more easier to visualize.
YoBuckStopsHere@lemmy.world 10 months ago
The magnets are not pulling it forward.
lsd@lemmy.world 10 months ago
The magnet is not pulling the car, the hand holding the magnet is pulling the car.
farfarawaay@sh.itjust.works 10 months ago
Okay. Maybe even dumb it down a little more? Just in case someone out there still doesn’t get it. Not me, I get it. Just someone else might not, and what about them you know?!
rockSlayer@lemmy.world 10 months ago
When the magnet got glued to the car, it became part of the car so it wouldn’t actually move. The reason it moves when it isn’t glued is because the hand keeps pulling the magnet away
wildcardology@lemmy.world 10 months ago
So the end of the video where the car is moving when the magnets are glued is just an editing trick?
gedaliyah@lemmy.world 10 months ago
Imagine a string instead of two magnets. If the hand pulls the string, the car moves. If the string is tied to the car?
MotoAsh@lemmy.world 10 months ago
Magnets transmit force, they don’t magically create energy. It takes energy to move the car, not just a static force being present. It’s the same as taping a stick to it without the magnets. Unless someone pulls on the stick (or magnet), no energy is entering the system and no work can be done.
kyle1320@lemmy.world 10 months ago
Just like the hanging magnet is pulling on the car, the car magnet is also pulling on the hanging apparatus. Unfortunately for the car, the apparatus is attached to it, so it all cancels out.
benignintervention@lemmy.world 10 months ago
Time to draw some free body diagrams!
Actually it would be the same force on the car if you removed the arm holding the magnet and placed a block of wood in the space between the magnets. It’s a static system