A penny falls from a windowsill 25.0 m above the sidewalk. How fast is the penny moving when it strikes the ground? (Remember that the velocity will be negative due to the downward motion of the penny)

To determine, the final velocity we use one kinematic equation. It would be 2ax = vf^2 - v0^2. The initial velocity would be zero since it starts from rest. Therefore, the equation would be:

vf = √ (2ax) where a is the acceleration (a = g) and x is the height

vf = √ (2) (9.8) (25)

vf = - 22.14 m/s