math
posted by melissa on .
really need help, i have no idea how to answer this question !
A stone is thrown off a cliff. it reaches a maximum height of 30m after 2 seconds, then falls into the water below. it hits the water after 5 seconds
a) how high above the water is the cliff ( The maximum height is relative to water level )
b) what is the ' second zero' and what does it mean

a. h + 30 = Vo + 0.5gt^2.
h + 30 = 0 + 0.5*9.8*5^2,
h + 30 = 122.5,
h = 122.5  30 = 92.5m. above the wate.
b. I'm not sure what they mean by "zeroes", but the inital velocity
is zero at the beginning of the free fall which is 30m above the top of the
cliff.