What happens when a person is on a swing with the gravitational potential and kinetic energies

Which describes an image that can be produced by a concave lens? the image is real and smaller than the object. the image is virtual and larger than the object. the image is virtual and smaller than the object. the image is real and larger than the object.

Apassenger walks toward the rear of a moving train. describe her motion as seen from a reference point on the train. then describe it from a reference point on the ground

Ryan is examining the energy of the particles in a bar of gold. what is ryan most likely studying?