Question

a tourist drops a rock from rest of a guard rail overlooking a valley. what is the velocity of the rock at 4.0 seconds

Answer 1

Answer: -39.2 m/s

Step-by-step explanation:

As soon as the rock leaves the tourist's hand, it will be in freefall. Since the rock will have a constant acceleration, we can use a kinematic equation to solve it.

`V_f = V_i + at`

Because the rock starts from rest, we know the initial velocity:

`V_i = 0 m/s`

Since the only force acting on the rock is gravity, we know that the only acceleration will be acceleration due to gravity:

`a = -9.8 m/s^2`

And we are given the time:

`t = 4.0 s`

We can simply plug these values into the kinematic equation to get the rock's velocity at 4.0 seconds:

`V_f = 0 m/s + (-9.8 m/s^2)(4.0 s)\\V_f = -39.2 m/s`