A 50-kg girl lifts a 1-kg box vertically upward a distance of 0.5 meter. How much work is done on the box?

Abird sitting high in a tree is an example of what type of wnergy

Consider a system to be two train cars traveling toward each other. what is the total momentum of the system before the train cars collide?   kg • what must the total momentum of the system be after the train cars collide?   kg •  

Auniform crate c with mass mc is being transported to the left by a forklift with a constant speed v1. what is the magnitude of the angular momentum of the crate about point a, that is, the point of contact between the front tire of the forklift and the ground