If pes represents the potential energy stored in a spring in kg . m^2 /s2 ,and x represents the change in spring length from its equilbrium position in m , what is the unitfor the spring constant k in the formula pes = 1/2 kx^2

Emmy kicks a soccer ball up at an angle of 45° over a level field. she watches the ball's trajectory and notices that it lands, two seconds after being kicked, about 20 m away to the north. assume that air resistance is negligible, and plot the horizontal and vertical components of the ball's velocity as a function of time. consider only the time that the ball is in the air, after being kicked but before landing. take "north" and "up" as the positive ‑ and ‑directions, respectively, and use ≈10 m/s2 for the downward acceleration due to gravity.