the weight does not matter for this question because the acceleration is the same for all object near the surface of the earth (g=10 m/s^2). so every second the object gains 10m/s of speed. the initial speed of the object is 0 and after 1 second it is 10. so the average speed of the object during the 1 second is: (10+0)/2 = 5 m/s. the distance travelled is the time interval ( 1 second) multiplied by the average speed ( 5 m/s): 1x5=5 m.
