# Ball drop question

1. Oct 8, 2008

### llee8820

1. The problem statement, all variables and given/known data
A ball of mass 0.35 kilograms is currently 1.1 meters off the floor and has a speed of 1.3 meters per second straight up. Assuming no energy is converted by air friction, how high will the ball go?

2. Relevant equations
PE=mgh
KE=1/2mv^2

3. The attempt at a solution
Since there is no friction or work, i set the equation as mgh=mgx+1/2mv^2, solving for x(final height) but I get the wrong answer. And I'm pretty sure this is the right equation to use.

2. Oct 8, 2008

### ice ace

yes I think that's a way to do it, maybe typo on calculator. I got 1.186m

3. Oct 8, 2008

### llee8820

1.186? How did u get that? These are the values I plugged in.
(.35*1.1*9.81)=(9.81*.35*x)+(.5*.35*1.3^2)
From this x=(((.35*1.1*9.81)-(.(5*.35*1.3^2))/(9.81*.35)
Using a Ti-83, and not rounding any answers, I get 1.014.

Im confused...

4. Oct 8, 2008

### ice ace

i think easier way is to use kinematics equation : vf^2=vi^2+2ad then add 1.1m with d to get it

5. Oct 8, 2008

### llee8820

Yup that did it. Thanks! Though I'm still wondering why my equations didn't work. O well, thanks for help

6. Oct 8, 2008

### llee8820

OMG nvm I'm a idiot. I can't do basic algebra -_____-, mine equation does work