# How hard will they hit the water?

• Jun 9th 2012, 07:48 AM
Shakey
How hard will they hit the water?
I apologise in advance if this should be somewhere else, but here goes anyways.

Me and a friend are making a film and at one point someone jumps off a bridge and onto a boat (but in the filming they will jump straight into the water). What I need to know is, will this hurt our actor? We hope to do the stunt twice (to make sure we have sufficient shots). First time round they will be jumping straight into the water. Second time around, we will be having a green screen on the water.

I have been able to work out a few things already using simple F=MA and Suvat, but these don't really include real world things like air resistance and such.

A few bits of info which I'm sure will help;

Actors weight 65kg
Bridge Height 4m
Density of Water 1000kg/m^3
Acceleration 9.81ms^-2

The Green screen will not be fixed just held in place lightly which will easily pull away once the actor lands on the screen.

Ben
• Jun 9th 2012, 08:15 AM
Reckoner
Re: How hard will they hit the water?
Quote:

Originally Posted by Shakey
Actors weight 65kg
Bridge Height 4m
Density of Water 1000kg/m^3
Acceleration 9.81ms^-2n

When you say "bridge height," are you talking about the actual height of the bridge, or the distance from the deck of the bridge to the water? In addition to the jump distance, the depth of the water is also a very important factor.

Unless the bridge is very low and the water reasonably deep, I recommend that you consider what you are doing very carefully. Impact with water at high speeds can be fatal. And even if the jump is within acceptable diving distance, impact with debris floating on the water (such as rocks or logs) can also be a source of injury or death. Finally, even if one survives the impact with the water's surface, the water must be deep enough for the diver to safely glide to a stop.
• Jun 9th 2012, 08:20 AM
Shakey
Re: How hard will they hit the water?
We are taking this very seriously and we are very aware of the potential dangers, but we haven't been able to survey the river bed just yet, we will also have sufficient waterside assistance (2 boats on the water and skilled first aided on the riverside.) Not to mention that our actor is skilled in this nature and knows what he is up against.

Ben