a 2-kg bowling ball sits on top of a building that is 40 m tall. which equation will you use to determine how much energy the object has?

gpe = mgh

ke = 1/2 m v2

both are needed

You don't need both. GPE is the gravitational potential energy caused by the fact that an object is not touching the ground of the earth. KE is caused by an object moving. This problem says that the bowling ball "sits" meaning that you only need the GPE because it's not moving and it is not touching the surface. You would use the GPE equation to find how much Potential energy an object has. If you want its velocity,  you would set the answer to the GPE equation equal to the KE equation to find its velocity.

chemical properties of thing