Answer:
5.72 seconds
848.27 m/s
97.94 m
Explanation:
t = Time taken
u = Initial velocity = 15 m/s
v = Final velocity
s = Displacement
a = Acceleration due to gravity = 9.81 m/s²
[tex]v=u+at\\\Rightarrow 0=15-9.81\times t\\\Rightarrow \frac{-15}{-9.81}=t\\\Rightarrow t=1.52 \s[/tex]
Time taken to reach maximum height is 0.97 seconds
[tex]s=ut+\frac{1}{2}at^2\\\Rightarrow s=15\times 1.52+\frac{1}{2}\times -9.81\times 1.52^2\\\Rightarrow s=11.47\ m[/tex]
So, the stone would travel 11.47 m up
So, total height stone would fall is 75+11.47 = 86.47 m
Total distance travelled by the stone would be 75+11.47+11.47 = 97.94 m
[tex]s=ut+\frac{1}{2}at^2\\\Rightarrow 86.47=0t+\frac{1}{2}\times 9.8\times t^2\\\Rightarrow t=\sqrt{\frac{86.47\times 2}{9.81}}\\\Rightarrow t=4.2\ s[/tex]
Time taken by the stone to travel 86.47 m to the water is is 4.2 seconds
The stone reaches the water after 4.2+1.52 = 5.72 seconds after throwing the stone
[tex]v=u+at\\\Rightarrow v=0+9.81\times 86.47 = 848.27\ m/s[/tex]
Speed just before hitting the water is 848.27 m/s
