Answer:
1.59 seconds
12.3 meters
but if you are wise you will read the entire answer.
Explanation:
This is a good question -- if not a bit unusual. You should try and understand the details. It will come in handy.
Time
Given
a = 0 This is the critical point. There is no horizontal acceleration.
d = 20 m
v = 12.6 m/s
Formula
d = vi * t + 1/2at^2
Solution
Since the acceleration is 0, the formula reduces to
d = vi * t
20 = 12.6 * t
t = 20 / 12.6
t = 1.59 seconds.
It takes 1.59 seconds to hit the ground
Height of the building
Givens
t = 1.59 sec
vi = 0 Another critical point. The beginning speed vertically is 0
a = 9.8 m/s^2 The acceleration is vertical.
Formula
d = vi*t + 1/2 a t^2
Solution
d = 1/2 a*t^2
d = 1/2 * 9.8 * 1.59^2
d = 12.3 meters.
The two vi's are not to be confused. The horizontal vi is a number other other 0 (in this case 12.6 m/s horizontally)
The other vi is a vertical speed. It is 0.
