i'm trying to calculate the impact force of a slide hammer under water. i can calculate it in air using (mv^2/2d), from work energy principle info i got off the net. and i have formulas for calculating drag; (0.5CpAv^2), also off the net, which i believe i have to account for? but no idea how to put them together really, differential?. i'm trying to do this to appropriately size a mems accelloremeter to measure force impact of a sediment corer. i thought if i work it out for air, it'd be less in water? but if i can work it out properly it'd be good. any help greatly appreciated. thanks in advance. j. mmm, looked into this abit more, not sure if i was going the right way about it? ideally want the answer in 'g' force. i don't think i could/can relate 'g' (accel force due to gravity) to force (newtons) on impact? or can i? it's all abit confusing example:if a weight drops 2m the velocity prior to impact i get is sqrt(2gh) = 6.26m/s^2. if it impacts and comes to rest over 0.1m, the deacceleration is v^2/2d = 196m/s^2. converting this to g-force i divide by 9.8m/s^2? this gives me 20g in this example. but i still have the problem of it all happening under water and the drag factor on the acceleration and deacceleration etc? am i making sense?