Gentlemen -

Love the show. However, there are a couple of things that I see you do repeatedly in the show that I do not believe are correct. I have not had physics in twenty years so please pardon any mistakes.

Cable Strengths
On several occasions a 10,000 lb test strength cable is destroyed to your amazement. This rating is typically for a static load, meaning that it could pick up a load that weighs 10,000 pounds. However, this rating is not for a dynamic load meaning that you could not drop a 10,000 pound weight a 10-20 feet and expect the cable to hold the load.

Along this same line there was a show where you had a primitive car frame that your brought to a sudden holt to see if a box of tissues as a projectile could cause bodily damage. Again you were amazed when it ripped the beam.

If memory serves the rule of physics that applies here is Force. Force = Mass * Acceleration. In a static load Acceleration is 0 so force is 0. Gravity is a common method of acceleration. Acceleration = (Change is Velocity) / (Change in Time). The key here is when you try to make a large change in velocity in a very small amount of time the force increases significantly! This is why the cables and devices you are grossly under rated and there is significant destruction. In many cases to include auto accidents, the manufactures try to provide some braking. Even the smallest amount can provide large reductions in the forces. For example, the crumpling of the front of the car to provide 5 feet or so of braking in an accident can be compared to taking your 10,000 pound steel cable and adding a elastic cord that can stretch 3 – 5 feet will provide the same effect.

In addition, in many cases where dynamic loads are in motion such as in tree work, they use ropes with some stretch factor rather than steel cable which has little to no stretch. The same applies to mountain climbing and other sports where a person may fall and need to be caught by the line. A little bit of stretch goes a long way.

Lastly, there was one show where you had two 18 wheel trucks collide head on into a car. Even though you dismissed this I believe there may be a few additional variables. First your vehicles impacted at 45 MPH. I do not know the parameters for the myth you were trying to reproduce, but around here most trucks run 75 MPH. Since the speed is related to kinetic energy which increases as a squared function of velocity, KE = Mass * (Velocity) * (Velocity) the amount of energy would be 2.7 times greater for each vehicle. To think of this in linear terms would be to image the force of the vehicles traveling at 121 MPH instead of 75 MPH. That gives you an ideal of how much additional Kinetic energy would be involved. Also, the load was very load in the bed of the trucks. I am inclined to believe that if the load was higher it may drive from the front of the cabs down into the vehicle rather than over the car. If you were to reproduce this experiment may I also suggest that you place a pulley at the end of the cable where the two tow trucks were positioned and use a separate cable between the trucks and around this pulley to provide the exact same force and speed to the two vehicles. This should also insure that they impact simultaneously.

Keep up the great work!