Which statements describe a situation in which work is being done? Check all that apply.

A box is carried up a flight of stairs by a mover.
A box sits on a table waiting to be moved.
Wind blows against a steel table anchored to the ground.
Wind blows a pool chair across the yard.
A weightlifter lifts a barbell off the ground.
A weightlifter holds a barbell above his head.

An object has a weight of 500 on earth what is the mass of this object

Two carts, one of mass 2m and one of mass m, approach each other with the same speed, v. when the carts collide, they hook together. assume that positive momentum is to the right. which graph best represents the momentum of both carts over time, before and after the collision?

Why does the equilibrium position of the spring change when a mass is added to the spring? will the mass oscillate around the new equilibrium position of the spring or the previous position without a mass attached to the spring? if the equilibrium position of the spring changes by 20 cm (assuming no initial mass) when a mass is added to the spring with constant 4.9 kg/s^2, what is the mass of the object attached to the spring?