A rock falls off the edge of a cliff that is 145 m above the ground beneath it. For how long a time is the rock falling? Assume air resistance is negligible.

A. 4.9 s
B. 2.9 s
C. 4.5 s
D. 3.3 s
E. 5.4 s

time=sqrt(2*145/9.8)

5.4 s

5.4s

To determine the time for the rock to fall, we can use the equation of motion for an object in free fall:

h = (1/2) * g * t^2

Where:
h is the height of the cliff
g is the acceleration due to gravity (approximately 9.8 m/s^2)
t is the time of fall

In this case, the height of the cliff is 145 m. We can rearrange the equation to solve for t as follows:

t = sqrt((2h) / g)

Substituting the values, we calculate:

t = sqrt((2 * 145) / 9.8) ≈ 5.441 s

Therefore, the time it takes for the rock to fall is approximately 5.441 seconds.

Since none of the answer choices match this value exactly, we round it to the nearest tenth. Therefore, the answer is E. 5.4 s.