Soon i dont understand this quiz

chuck drops a rock from a height of 70 m. how long will it take the rock to hit the ground?

use the formula h(t)=−4.9t^2+v0t+h0, where v0 is the initial velocity and h0 is the initial height.

round to the nearest tenth of a second. enter your numeric answer.

1. h₀ = 70  

v₀ = 0 since the rock is dropped it has no initial velocity  

when the rock hits the ground the height = 0  

plug into the formula  

0 = -4.9t² + 0(t) + 70  

0 = -4.9t² + 70  

Add 4.9t² to both sides  

4.9t² = 70  

Divide both sides by 4.9  

t² = 14.2857142857  

Take the square root of both sides  

t = 3.7796447301  

t ≈ 3.8 seconds

I am not doing the rest I only did one just to help you understand a bit more