Suppose Keiji is standing at the base of a hill, and Nia is standing at the top of the hill, both facing towards the hill's peak. If Keiji throws his hat straight up into the air, what will Nia observe about the motion of the hat?

Provide a very brief response.
Nia will observe that the hat moves straight upward and then straight back down from Keiji's position. Because gravity acts downwards towards the center of the Earth, it will pull the hat back down after it reaches its highest point. Even though Nia is higher up on the hill, the force of gravity still acts on Keiji's hat in the same way, making the hat's movement appear vertical from her perspective as well. The hill's slope does not affect the vertical motion of the hat relative to Keiji.