Momentum Change in a Collision with Combined Units

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In summary, this conversation discusses the calculation of change in momentum for two objects before and after a collision. There is a discrepancy in the results due to the combined unit traveling after the collision. The problem lies in the insufficient data, specifically the unknown masses of the two objects, which prevents the calculation of individual changes in momentum.
  • #1
sameeralord
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In this collision


Before= p=100 kg m/s---> <-----p=120 kg m/s
After= <--combined unit P= 20 kg m/s

In this question when I work out the change in momentum for 2 objects it is not the same. When there is a combined unit traveling after the collision can't you find the change in momentum?
 
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  • #2
What's the problem? The total momentum is 20 kg-m/s to the left both before and after the collision.
 
  • #3
phyzguy said:
What's the problem? The total momentum is 20 kg-m/s to the left both before and after the collision.

How do you find the change in momentum of each object? Is the data insufficient?
 
  • #4
I see your question. Unless you know the masses of the two objects, you don't know how much of the final momentum belongs to each object, so you can't calculate the individual changes.
 
  • #5


Yes, in this scenario, the change in momentum cannot be calculated using the traditional formula of mass times velocity (p=mv). This is because the combined unit after the collision does not have a singular mass or velocity, but rather a combination of the two objects' masses and velocities.

To find the change in momentum, you would need to use the principle of conservation of momentum, which states that the total momentum before the collision is equal to the total momentum after the collision. This means that the change in momentum is equal to the difference between the total momentum before and after the collision.

In this case, the total momentum before the collision is 100 kg m/s + 120 kg m/s = 220 kg m/s. After the collision, the combined unit has a momentum of 20 kg m/s. Therefore, the change in momentum is 220 kg m/s - 20 kg m/s = 200 kg m/s.

It is important to note that in this scenario, the units for momentum are still kg m/s, as they represent a combination of mass and velocity. However, the change in momentum is a scalar quantity, so it does not have a direction associated with it.
 

1. What is momentum?

Momentum is a scientific concept that describes the quantity of motion an object has. It is determined by an object's mass and velocity, and is a vector quantity, meaning it has both magnitude and direction.

2. How is momentum calculated?

Momentum is calculated by multiplying an object's mass by its velocity. The formula for momentum is p = m * v, where p is momentum, m is mass, and v is velocity. The standard unit of momentum is kilogram meters per second (kg*m/s).

3. What is the law of conservation of momentum?

The law of conservation of momentum states that in a closed system, the total momentum remains constant. This means that the total momentum before a collision or interaction is equal to the total momentum after the collision or interaction. This law is based on the principle of inertia and is a fundamental principle in physics.

4. How does momentum relate to Newton's laws of motion?

Momentum is closely related to Newton's laws of motion. The first law of motion states that an object will remain at rest or in motion at a constant velocity unless acted upon by an external force. The second law of motion states that the acceleration of an object is directly proportional to the net force acting on it and inversely proportional to its mass. The third law of motion states that for every action, there is an equal and opposite reaction. Momentum helps to quantify these laws and understand the effects of forces and motion on objects.

5. How is momentum used in real life?

Momentum has many practical applications in real life. It is used in sports, such as calculating the momentum of a ball in motion, and in transportation, such as the momentum required to launch a rocket into space. Momentum is also important in car safety, as it helps determine the force of impact during a collision. Additionally, understanding momentum is crucial in engineering and design, as it helps predict the movement and stability of structures and machines.

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