Magneto was right!

It will work fine of your intention is to secure the arm so that it won't dangle when you drive

Go (back) to school

the car already has metal in it, so the metal block is unnecessary

For the same reason why this device does not go left by the metal slab pulling the magnet to the left

What's funny is this would actually work if you just pointed the magnet at other people's cars.

After hitting too many children the tires will get stuck.

The CIA puts backdoor code in all the magnets to prevent this from working. Source: trust me bro.

This illustration does not imply that the car is moving. There are no "speed lines" or arrows that would indicate that.

So the illustrated setup would 100% work.

It's actually a common misconception that magnets always attract metal. This misconception was popularized by people joking that magnets are magic. In reality, magnets attract because they have magnetions in them. These magnetions allow them to attract things like metal but a little bit is used up each time. Eventually once the magnet's magnetions have been depleted, the magnet turns back into a newt and goes home to recharge.

I built a scale model to prove the haters wrong. I had to tilt the platform a little for it to overcome friction, but once I did, the car rolled forward until it hit a wall.

Magnets don't do work

Less fun at parties guy: While the diagram leaves it somewhat unclear as to what precise effect that mechanism is intended to achieve, clearly it involves electromagnetism and thus any proper explanation must begin with a full description of quantum field theory...