Question

Bill kicks a rock off the top of his apartment building. it strikes a window across the street 13 m away. the acceleration of gravity is 9.8 m/s 2 . if the window is 25 m below the position where bill contacted the rock, how long was it in the air? answer in units of s.

Answer 1

This problem fall under the "equations of motion" the formula to follow on this problem is "d=Vit + 1/2gt²". The initial Velocity of the rock will be Zero, Therefore Vi=0 Distance d=25m, g=9.8m/s². Since Vi=0 cancel it to the equation above. The equation will be d=1/2gt². Solve for time "t' the final equation will be t=√2d/g or t=√2(25m)/9.8m/s²= (ans in seconds)

Answer 2

Refer to the diagram shown below.

The vertical distance traveled is
s = 25 m

The initial vertical launch velocity is zero.
Therefore
s = (1/2)*g*t²
where g = 9.8 m/s²
t = the time of flight, s

That is,
0.5*9.8*t² = 25
t² = 25/4.9 = 5.102
t = 2.26 s

Answer: 2.26 s