A rock is thrown horizontally off a 20m tall cliff with a prosody of 20 m/s what is the final velocity of the rock on the impact ( magnitude and direction)?

28.3 m/s 45° below horizontal

Explanation:

Given in the y direction:

Δy = -20 m

v₀ = 0 m/s

a = -10 m/s²

Find: v

v² = v₀² + 2aΔy

v² = (0 m/s)² + 2 (-10 m/s²) (-20 m)

v = -20 m/s

In the x direction, acceleration is 0, so v = v₀ = 20 m/s.

The magnitude is found with Pythagorean theorem:

v² = (20 m/s)² + (-20 m/s)²

v = 28.3 m/s

The direction is found with trig:

θ = atan(-20 m/s / 20 m/s)

θ = -45°