I have put some coal into it, but I can’t move the cart…
… You grab it with G.
Why did you put coal in it?
Maybe its too heavy?
Well coal pallets, and I wanted to bring them back and see what happens when I set them on fire.
Those are roughly 13kg each, so you probably wouldn’t need to load up too many of them before you couldn’t drag the cart anymore. If the cart and contents are more than 5x your lift capacity, it should be printing the message “The Shopping Cart is too heavy for you to budge!” to the log.