Which two phases describe the nature of an electromagnetic force ?

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

Give an example in which the electrical energy changes to light energy

Using the free-body diagram, calculate the net force acting on the sled. is the sled in a state of dynamic equilibrium?