Final answer:
To find the height of the cliff, use the equation of motion for free fall. Given the initial velocity of the ball and the time it takes to hit the ground, calculate the height of the cliff using the equation.
Step-by-step explanation:
To find the height of the cliff, we can use the equation of motion for free fall. The equation is given as:
h = (1/2)gt^2 + v0t + h0
Where h is the height, g is the acceleration due to gravity (-9.8 m/s²), t is the time, v0 is the initial velocity, and h0 is the initial height.
In this case, we have v0 = 20 m/s, t = 4.0 s, and h0 = 0 (since the ball is thrown from the top of the cliff). Plugging in these values, we can calculate the height of the cliff.
h = (1/2)(-9.8)(4.0)^2 + (20)(4.0) + 0 = -78.4 + 80 + 0 = 1.6 m
Therefore, the height of the cliff is 1.6 meters.