Answer: -39.2 m/s or 39.2 m/s directed downwards
Explanation:
This situation is a good example of Free Fall, where the main condition is that the initial velocity must be zero [tex]V_{o}=0[/tex], and the acceleration is constant (acceleration due gravity).
So, in order to calculate the final velocity [tex]V[/tex] of the rock just at the moment it hitsthe bottom of the cliff, we will use the following equation:
[tex]V={V_{o}}^{2}+gt[/tex]
Where:
[tex]g=-9.8 m/s^{2}[/tex] is the acceleration due gravity (directed downwards)
[tex]t=4 s[/tex] is the time it takes to the rock to fall down the cliff
[tex]V=(-9.8 m/s^{2})(4 s)[/tex]
[tex]V=-39.2 m/s[/tex] This is the rock's final velocity and its negative sign indicates it is directed downwards
Explanation:
It is given that,
Initial speed of the rock, u = 0
It hits the bottom of the ravine at 4 seconds. Let v is the speed of the rock when it hits the bottom of the cliff. It will move under the action of gravity. Using equation of kinematics as :
[tex]v=u+at[/tex]
a = g
[tex]v=u+gt[/tex]
[tex]v=gt[/tex]
[tex]v=9.8\ m/s^2\times 4\ s[/tex]
v = 39.2 m/s
So, the speed of the rock when it hit the bottom of the cliff is 39.2 m/s. Hence, this is the required solution.
