Astudent makes a simple pendulum by attaching a mass to the free end of a 1.50-meter length of string
suspended from the ceiling of her physics classroom. she pulls the mass up to her chin and releases it from
rest, allowing the pendulum to swing in its curved path. her classmates are surprised that the mass doesn’t
reach her chin on the return swing, even though she does not move. explain why the mass does not have
enough energy to return to its starting position and hit the girl on the chin.