Physics
posted by Andrea .
a ball is released from rest and rolls down in an inclined plane, requiring 4 sec. to cover a certain distance of 100m. a) what is the acceleration?
b) how many cm would it have fallen vertically in the same time?

We will be glad to critique your thinking, but don't have time to do all your work for you. The average speed (25 m/s in this case) tells you that the final velocity 50 m/s. Divide that by the elapsed time for the aceleration.
I am sure you know the formula for the time to fall Y vertically.
Y = (1/2)g t^2
Use it. You may have to convert meters to cm. 
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a) a=2(distance)/time^2
= 2(100cm)/16s^2
=12.5 cm/s^2
b) s= (gt^2)/2
since g = 9.8 m/s^2
= (9.8 x 16)/2
=78.4 m
or 7840 cm 
a) a=2(distance)/time^2
= 2(100cm)/16s^2
=12.5 cm/s^2
b) s= (gt^2)/2
since g = 9.8 m/s^2
= (9.8 x 16)/2
=78.4 m
or 7840 cm