Question by geklein3: How to solve vertical motion equations?
the problem is:
Cliff diving. A cliff diver jumps from a ledge 96 feet above the ocean with an initial upward velocity of 16 feet per second. How long will it take until the diver enters the water? Use the equation h=-16t^2+vt+s, where v+ initial vertical velocity and h+ initial hight.
Thanks for the help!
Best answer:
Answer by mathgirl
I think you have your variables a little confused. If you are using the equation:
h = -16t^2 +vt + s
then
h = height of the diver (in feet) at time t (in seconds)
t = time (in seconds)
v = initial vertical velocity (in ft/s)
s = initial height (in feet)
So, you are given the following information,
v = 16 ft/s
s = 96 ft
Put the information you are given into the equation and you get:
h = -16t^2 + 16t + 96
You are asked to find the time (t) when the diver enters the water (when h = 0 ft). So, set h=0 and solve for t:
0 = -16t^2 + 16t + 96 … divide both sides by -16
0 = t^2 – t – 6 … either use quadratic formula or factor to solve
0 = (t – 3)(t + 2)
t = 3 or -2
Since we are looking for the time it took to reach the water, we can logically throw out the negative number, and we get an answer of 3 seconds.
Hope that helps!
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