How do you lift this huge rock? With a simple machine like this lever. Jeff steps on one end of the lever, pushing down and the
rock is lifted up. What is the mechanical advantage of using this
lever?

Assume you measured the mass of the cart to be (500 ± 1) g and the mass of the additional mass you put on the cart to be (500 ± 1) g as well. since the scale you are using in the lab cannot measure objects heavier than 600g you will have to sum up individual pieces and propagate the error. so what would be the mass and the standard error of the cart and the mass