Final answer:
To calculate the height of the cliff, use the equation for the distance an object travels when dropped, with a runtime of 4.2 seconds. The height of the cliff is approximately 86 meters.
Step-by-step explanation:
To calculate the height of the cliff, we can use the equation for the distance an object travels when dropped:
distance = (1/2) * acceleration due to gravity * time^2
Since the stone is dropped, the initial velocity is 0, so we can simplify the equation to:
distance = (1/2) * 9.8 m/s^2 * (4.2 sec)^2
Solving for distance, we get:
distance = 0.5 * 9.8 m/s^2 * 17.64 sec^2 = 86.148 m
Therefore, the height of the cliff is approximately 86 meters, which corresponds to option b.