how fast are the divers going when they hit the water?

Question

The cliff divers at Acapulco, Mexico, jump off a cliff 25.2 m above the ocean. Ignoring air resistance, how fast are the divers going when they hit the water?

Answer 1

height = h(t) = -4.9t^2 + 25.2 = 0 when they hit the water

solve for t

t^2 = 25.2/4.9 = about 5.14

t = sqr5.14 = about 2.3 seconds

velocity is the derivative of acceleration or v = -9.8t = -9.8(2.3) at time hitting the water

v = a' = -22.5 meters per second

assuming no arithmetic mistakes on the way.

the negative sign for v indicates downward movement.