Optimizing Steel Cable Strength for Stopping a 17,000 lb Vehicle at 10mph

  • Thread starter Thread starter swoodbury
  • Start date Start date
  • Tags Tags
    Forces Impact
AI Thread Summary
To determine the necessary tensile strength of the steel cable for stopping a 17,000 lb vehicle at 10 mph, it is crucial to consider the conservation of momentum and energy. The stopping distance is not negligible, as a sudden stop would require infinite force, thus complicating the calculations. The interaction time during the impact significantly influences the forces involved, necessitating experimentation to accurately assess the required cable strength. Additionally, the design must account for the potential rebound of the vehicle, which could affect the effectiveness of the barrier system. Overall, a thorough analysis involving both momentum and energy principles is essential for a reliable solution.
swoodbury
Messages
1
Reaction score
0
I have a complicated problem I'd like some assistance with.

I have a 17,000 lb vehicle traveling at 10mph and impacting a series of 4000lb jersey barriers connected by a 1" steel cable through the inside of the jersey barriers. The cable will be anchored at each end by 22,000lb blocks. The spacing in between the jersey barriers is 30 inches. Total length of jersey barrier and cable configuration is 100ft. What is the tensile strength of the steel cable I need to stop the vehicle? Distance required to stop the vehicle is negligible, I just need it to stop! Assume modulus of elasticity of the steel in tension is 28 x 10^3 ksi.

I'm stumped and any help would be greatly appreciated!
 
Physics news on Phys.org
A diagram would or figure would be greatly appreciated..! ;-)
 
Welcome to PF;
The distance required to stop the vehicle is never negligible - the shorter the distance the more energy is expended: to stop a vehicle dead in zero distance requires infinite force.

But you should be able to work the problem in terms of conservation of momentum.
This should give you an idea pf the energies involved and thus the energy that needs to get absorbed by the cable and thus the tensile strength.
 
The answer to any problem such as this one will depend upon the time taken for the interaction. This is because the Momentum change is Force times time (Impulse). You would need a lot of experimenting if you wanted to find out the actual forces involved. There are so many unknowns in your model, so far.

The OP reads as if it could be seeking to analyse what went on in an accident. To make any argument stand up in court, you need a highly paid 'expert' to convince a Judge. The sum total of PF knowledge of the subject will never convince that guy. (Just so that you won't be disappointed, later.)
 
Since we have elastic cables, I think you need both conservation of momentum and energy.
 
In the case of such a collision, can we really expect the impacting vehicle to rebound with a significant amount of KE? That would sound to be a very dodgy way to design a barrier. Boing! boing!
 

Thread '1:1 versus 2:1 Mechanical Advantage debate'

The rope is tied into the person (the load of 200 pounds) and the rope goes up from the person to a fixed pulley and back down to his hands. He hauls the rope to suspend himself in the air. What is the mechanical advantage of the system? The person will indeed only have to lift half of his body weight (roughly 100 pounds) because he now lessened the load by that same amount. This APPEARS to be a 2:1 because he can hold himself with half the force, but my question is: is that mechanical...
View full post »

Thread 'Average velocity as a weighted mean'

Hello everyone, Consider the problem in which a car is told to travel at 30 km/h for L kilometers and then at 60 km/h for another L kilometers. Next, you are asked to determine the average speed. My question is: although we know that the average speed in this case is the harmonic mean of the two speeds, is it also possible to state that the average speed over this 2L-kilometer stretch can be obtained as a weighted average of the two speeds? Best regards, DaTario
View full post »

Thread 'Newton's first law?'

Some physics textbook writer told me that Newton's first law applies only on bodies that feel no interactions at all. He said that if a body is on rest or moves in constant velocity, there is no external force acting on it. But I have heard another form of the law that says the net force acting on a body must be zero. This means there is interactions involved after all. So which one is correct?
View full post »

Hot Threads

Recent Insights

Back
Top