An object falls from rest. While falling it changes its speed by 10 meters per second every second. Calculate how far it has fallen, in meters, after falling for 4 seconds. However, do not put the units in the box below.
a = 10 m/s^2
v = a t = 10 t
x = (1/2) a t^2 = 5 t^2
so if t = 4
x = 5 (16)
= 80