A hot-air balloon is rising upward with a constant speed of 3.93 m/s. When the balloon is 4.91 m above the ground, the balloonist accidentally drops a compass over the side of the balloon. How much time elapses before the compass hits the ground?

h = -3.93t * 4.9t^2 = 4.91 m.

4.9t^2 - 3.93t - 4.91 = 0
Use Quadratic Formula and get:
t = 1.48 s.

To find the time it takes for the compass to hit the ground, we need to calculate the time it takes for the compass to drop from a height of 4.91 m.

We can use the kinematic equation for vertical motion:

Δy = v₀t + (1/2)gt²

where:
Δy = change in height (4.91 m)
v₀ = initial velocity (0 m/s since the compass is dropped)
t = time
g = acceleration due to gravity (approximately 9.8 m/s²)

Rearranging the formula, we get:

t = √(2Δy / g)

Now, we can substitute the given values:

t = √(2 * 4.91 m / 9.8 m/s²)

t = √(0.999 m / 9.8 m/s²)

t ≈ 0.45 seconds

Therefore, it takes approximately 0.45 seconds for the compass to hit the ground.