A hot air balloon is rising upward with a constant speed of 15 m/s. When the balloon is 4 m above the ground, the balloonist accidentally drops a compass over the side. What is the speed before it hits the ground? And How high above the ground is the balloon when the compass hits the ground?

1. Use v^2 = u^2 +2as[/math] to find the speed at which it hits the ground.

You have u, a and s. You can solve for v.

2. Use s=ut+\frac12 at^2

It's a quadratic equation that you solve using the formula

x = \frac{-b \pm \sqrt{b^2 -4ac}}{2a}

With that, you found the time elapsed. In that time, you can find the additional distance covered by the balloon using s = ut

Then, add that s with 4 m to have the distance from the ground of the balloon.

Hope it helped! :)