If the net force acting on an object doubles, how will the object’s acceleration be affected?

Lets say that an object of a certain volume has a certin mass. what happens to its mass when you double its volume?

An object moves from position +34m to the position -15m in 15 seconds. what is the total displacement? what is the total velocity?

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