# A ball is dropped from the top of a building...

1. Sep 16, 2018

### Peter Groppino

1. The problem statement, all variables and given/known data
A ball is dropped from the top of a building and falls vertically downwards. Air resistance can be neglected. After falling a distance d, the speed of the ball is v. Determine the speed of the ball (in terms of v) when it has fallen a distance of 2d.

2. Relevant equations

3. The attempt at a solution
We tried to isolate for V2 and d and then substitute them into each other but that didn't work. Please help!

2. Sep 16, 2018

### FactChecker

You should show the relevant equations and what you did with them in your work.

3. Sep 16, 2018

### Peter Groppino

I'm sorry but whats a relevant equation? a=9.8m/s2 and V1=0m/s and I'm not sure what to put for d and V2 which is what we are solving for. Not sure if that helps?

4. Sep 16, 2018

### vela

Staff Emeritus
Can you identify what kind of problem this is, e.g., what concepts are relevant? What do you mean by "university acceleration" in the title? You're referring to $d$, $v_1$, and $v_2$. The variable $d$ is defined in the problem statement, but we'd have to guess what you mean by $v_1$ and $v_2$.

5. Sep 16, 2018

### Peter Groppino

Im sorry im in grade 12 doing a "University" question. I just wrote down what the question asked me. I have no clue what to do. Sorry

6. Sep 16, 2018

### PeroK

Hint: Distance is the area under a graph of speed against time.

7. Sep 16, 2018

### jbriggs444

We are given information on both the distance fallen and on the final velocity. From that information [and an assumption of constant acceleration] it is possible to write down an expression for the actual acceleration. That acceleration might not be 9.8 m/s2.

What are some equations that you know for motion under constant acceleration? Or for work, momentum and kinetic energy?