Momentum Theory To Solve Car Crash?

In summary, the conversation discusses a problem involving a collision between two vehicles, one moving at a high speed and the other at a slower speed. The question is posed as to how fast the high-speed vehicle was traveling. Suggestions are made to use momentum theory and consider factors such as friction and forces decelerating the vehicles. However, given the lack of information, it is difficult to solve the problem. The conversation concludes with further thoughts and questions on the problem.
  • #1
Gordon Arnaut
16
0
I wonder if someone might suggest an approach to solve this problem?

A vehicle weighing 5000 lbs is moving at 10 mph and is struck from behind by a vehicle weighing 5000 lbs and moving at a high rate of speed. The slow-moving vehicle is pushed forward a distance of 150 feet.

How fast was the high-speed vehicle traveling?

I suspect we can apply momentum theory to solve this, but am having trouble getting started.

Regards,

Gordon.
 
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  • #2
There is missing information here, unless they want you to solve in terms of something, rather than get a specific answer (which I doubt).

Does it mention anything about a frictional force between the road and tires?

To apply the fact that the slow-moving car traveled 150 feet further than the point of the collision, we would need to know the forces decelerating the moving couplet of vehicles.

By using the equation (m_a)*(v_a) + (m_b)*(v_b) = (m_c)*(v_c), where c = the cars while combined, we can plug in the masses of both objects and the known speed. On the other side of the equation, we'd add the masses and have v_c as an unknown. This is where we run into trouble--two unknowns and no other ways to find them (unless this is not as easy of a problem as I had thought it was). I cannot find any way to solve this problem. Make sure you're supplying all the details.
P.S. Wrong forum. Post it in the homework section.
 
  • #3
No, this is not an easy problem.

The tire friction was not given, but this is probably something that could be looked up.

I'm not sure it would come into play that much anyway.

Let's take a similar problem, where you have a fast-moving vehicle that hits a boulder and sends it flying through the air. Here the force opposing the movement of the boulder is simply gravity and its inertia.

If we simplify our problem with the two vehicles by assuming one is standing still when it is hit, perhaps we can find a way into it.

Regards,

Gordon.
 
  • #4
Are you assuming that the slower car locked up the tires at the point of collision? If not, the car could have just kept rolling at a slow speed.
 

1. What is momentum theory in relation to car crashes?

Momentum theory is a physics principle that states that the total momentum of a system remains constant, unless acted upon by an external force. In the context of car crashes, it explains the behavior and outcome of collisions based on the momentum of the vehicles involved.

2. How does momentum theory help in understanding car crashes?

Momentum theory helps in understanding car crashes by providing a quantitative approach to analyzing and predicting the outcome of collisions. It takes into account factors such as the mass and velocity of the vehicles, and the direction and angle of impact, to determine the resulting momentum and potential damage.

3. Can momentum theory be used to prevent car crashes?

Momentum theory itself cannot prevent car crashes, but it can be used to inform and improve safety measures and regulations. By understanding the principles of momentum, engineers and policymakers can design and implement measures such as speed limits, seatbelts, and airbags to decrease the impact and severity of car crashes.

4. Is momentum theory the only factor in car crashes?

No, momentum theory is not the only factor in car crashes. Other factors such as friction, force, and energy also play a role in determining the outcome of collisions. Additionally, human error and external conditions such as weather and road conditions can also contribute to car crashes.

5. How can momentum theory be applied in accident reconstruction?

Momentum theory is commonly used in accident reconstruction to determine the speed and direction of vehicles involved in a crash. By analyzing the resulting momentum and damage, investigators can piece together the sequence of events leading up to the collision and determine the cause and responsibility for the crash.

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