Here's my problem: I have to find how much deceleration & how deep it will be when something fall into the water, but I just have the Vo when it strikes the water and of course Vt which is 0. I dunno how can I measure its deceleration underwater. OK, actually I just want to know how much force that the water gives when this thing strikes the water. So, I wanna combine the equation F.t= m(Vt-Vo). Can I use that? But I have to get either the time and I'll use Vt=0, or the Vt and I'll use the time = 0.01 s, so it's just instanteous velocity. What equation should I use??? Please help me, it's a part of my project and if I can't solve this problem, it mean I should change the whole project!