In a bizarre but harmless accident, super man fell from the eiffel tower. how fast was superman traveling when he hit the ground 7.80 seconds after falling?

The acceleration of gravity here on our home-planet is 9.8 m/s².

That means that at any time during the fall, a falling object is falling
9.8 m/s faster than it was 1 second earlier. 

Looking at it another way, the speed of any falling object increases
by 9.8 m/s every second while it falls.

If Superman fell for  7.8 seconds, then his falling speed gained

                             (7.8) x (9.8 m/s)  =  76.44 m/s

during the time he spent falling.

Since his falling speed was zero when he 'stepped' off of the top,
he hit the ground at  76.44 m/s .

Note: 
That's about 170 miles per hour.
I'll bet he left one serious crater !

Did you ever figue this