I could use some help with the following Physics question.

A powerful motorcycle can accelerate from rest to 24.8 m/s (55 mi/h) in only 3.90 s. (For each answer, enter a number.) (a) What is its average acceleration in m/s2? m/s2 (b) How far (in m) does it travel in that time? m (a) Calculate the height (in m) of a cliff if it takes 2.28 s for a rock to hit the ground when it is thrown straight up from the cliff with an initial velocity of 8.17 m/s. (Enter a number.) m (b) How long (in s) would it take to reach the ground if it is thrown straight down with the same speed? (Enter a number.)