A cliff diver horizontally runs off a 12 m high cliff at 10 m/s. How far away does he land?
25.5 m
15.5 m
10.5 m
98.0 m

15.5 m (second answer listed)

Explanation:

Start by calculating the time it takes the diver to get to the bottom of the cliff knowing there is no vertical component in hos velocity, so we treat the vertical motion as free fall. In free fall:

y = -1/2 g t^2

for this particular case:

- 12 = - 4.9  t^2

t^2 = 12/4.9

t^2 = 2.4489

t = 1.565  sec

Now we use the calculated time in the equation of horizontal motion:

x = v t

x = 10 * 1.565

x = 15.65 m

Then, the closest answer is the second one listed

3. dark matter

empty space could also be a simple vacuum