# Time it take for small objects to come together under gravity

1. Jan 25, 2007

### hover

Hey everyone!!

I've done this experiment and i find it interesting how objects of any mass just randomly attract each other. Anyway, i always wanted to find out how long it should take for a mass in this experiment to gravitate towards the other. The problem is it isn't like doing it on earth where at the surface everything accelerates at 9.8m/s. The only relevant equation for acceleration in this case would be
G*M/r^2
G=6.67*10^-8cm³/g-sec²
m=mass in grams
r=distance in cm
I just learned a LITTLE calculus but so far i can only calculate how long it will take for an dropped object to hit the ground. I was hoping i could use this but since the acceleration is always changing i don't know how to do this out. Can someone help??

Thanks

2. Jan 25, 2007

### ranger

Hi hover,

Really? Where you expecting them to repel each other

So you want to complicate things more with non constant acceleration I see. I dont know the extent of your calculus knowledge, but this involves integrating the acceleration function.

http://www.sunybroome.edu/~biegen_j/phys1/modules/varacc/Mod4_3.htm
http://hyperphysics.phy-astr.gsu.edu/hbase/avari.html

I recommend for situations like this, you should use constant acceleration and find the time like you would normally.

Last edited: Jan 25, 2007