a boy throws a ball straight up into the air. it reaches its highest point after 4 seconds. how fast was the ball going when it left the boy's hand​

Explanation:

The most important thing to remember about parabolic motion in physics is that when an object reaches its max height, the velocity right there at the highest point is 0. Use this one-dimensional motion equation to solve this problem:

v = v₀ + at and filling in:

0 = v₀ + (-9.8)(4.0) **I put in 4.0 for time so we have more than just 1 sig fig here**

0 = v₀ - 39 and

-v₀ = -39 so

v₀ = 39 m/s

wire in brush may conduct electricity from cell to drill and vice versa electrc shock possible

it has to be b, about 97 percent.