What is the potential energy of a 3gram penny atop the empire state building (381m)

Explain why electric current cannot exist if a current doesn't have a voltage source.

Suppose you plot the distance traveled by an object at various times and you discover that the graph is not a straight line. what does this indicate about the object's acceleration?

Your friend increases her force on the desk by 30n . she doesn't change the direction of her push . what happens to the net force on the desk .will the desk accelerate