- #1

Ineedhelpwithphysics

- 42

- 7

- Homework Statement
- When I drop a rock from the top of my ladder, I notice that it takes 0.25 seconds for the rock to fall past our 2-m tall door and hit the ground below. What was the velocity of the rock when it passed the top of the door?

- Relevant Equations
- vf = v0 + at

∆x = v0t + 1/2 at^2

I am super stumped at this question, the answer key is telling me 6.78 downwards, i think I'm reading and observing the question wrong. Isn't final velocity 0 so why can't i do

0 = v0 -9.8(0.25)

-2.45 = v0

But when I use the second the equation

-2 (displacement of door) = v0(0.25) + 1/2 (-9.8)(0.25)

-6.75 = v0

Why am i getting two answers, it's clear the first equation is wrong but why is that? is the final velocity not zero, but it hit the ground and hitting the ground means 0 velocity.

0 = v0 -9.8(0.25)

-2.45 = v0

But when I use the second the equation

-2 (displacement of door) = v0(0.25) + 1/2 (-9.8)(0.25)

-6.75 = v0

Why am i getting two answers, it's clear the first equation is wrong but why is that? is the final velocity not zero, but it hit the ground and hitting the ground means 0 velocity.