Can any one help please? i'm convinced my time is correct.
A rock is thrown horizontally from a cliff with a speed of 15 m/s. It falls half the height of the cliff in the last three seconds of its fall. What is the total fall time? (use g = 9.81 m/s^2)
This is my attempt, since the rock is thrown horizontally it makes no difference to the fall time.
so:
Can you please confirm?
Hello, 1LISTEN!
A rock is thrown horizontally from a cliff with a speed of 15 m/s.
It falls half the height of the cliff in the last three seconds of its fall.
What is the total fall time? .(Use g = 9.81 m/sē) . ← Also not needed
Since the rock is thrown horizontally its initial speed
makes no difference to the fall time. . . . . . Right!
The height of an dropped object is: .
. . where = initial height.
In the first seconds, the rock falls half the height: .
. . .[1]
In the next 3 seconds, the rock strikes the ground: .
. . .[2]
Equate [1] and [2]: .
Quadratic Formula: .
Therefore, the total fall time is: . seconds.