A 0.5 kg rock is dropped from the edge of a 52-foot cliff. How fast will it be going when it hits the ground at the base of the cliff?
A) ft/s
B) ft/s
C) 52 ft/s
D) ft/s

Question

A 0.5 kg rock is dropped from the edge of a 52-foot cliff. How fast will it be going when it hits the ground at the base of the cliff?
A) ft/s 
B) ft/s 
C) 52 ft/s 
D) ft/s

Quizplus · Accepted Answer

We can solve this using the formula:

v^2 = u^2 + 2as

Where:
v = final velocity (what we want to find)
u = initial velocity (which is 0 because the rock is dropped)
a = acceleration due to gravity (which is -9.8 m/s^2)
s = distance fallen (which is 52 ft or 15.85 m)

So, plugging in the values:

v^2 = 0 + 2(-9.8)(15.85)
v^2 = -311.08
v = √(-311.08) (we take the square root of both sides, noting that the answer is imaginary due to the negative value)
v = 17.64i

We can convert this to feet per second:

v = 17.64i * 3.28 ft/m
v = 57.94 ft/s

Rounding to two significant figures gives us:

v = 58 ft/s

Therefore, the closest answer choice is B.

A 05 Kg Rock Is Dropped from the Edge of a a 52-Foot