# Momentum Flux: Quick Question (Product Rule)

• andrew.c
In summary, momentum flux is a measure of the transfer of momentum between objects, calculated by multiplying the velocity by the force acting on the object. The product rule for calculating momentum flux states that the total momentum flux is equal to the sum of the individual momentum flux of each object. Momentum flux is related to Newton's Third Law of Motion, as it represents the transfer of momentum between objects in a collision. In physics, momentum flux is important for understanding and predicting the motion of objects, and it is measured or calculated in experiments using instruments such as force sensors and accelerometers.
andrew.c

## Homework Statement

Heya,
I can expand the term on the LHs and get the term on the RHS no problem :)
But,
I don't understand how the bottom line is arrived at; I think its basically just a backward engineering of the product rule, but I can't get it!

Any help would be useful

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• momentum flux.JPG
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$$\frac{\partial(\rho u u)}{\partial x} = \rho u \frac{\partial u}{\partial x} + u \frac{\partial (\rho u)}{\partial x}.$$

Thanks
That was easier than I thought!

## 1. What is momentum flux?

Momentum flux is a measure of the transfer of momentum from one object to another. It is calculated by multiplying the velocity of the moving object by the force acting on it.

## 2. What is the product rule for calculating momentum flux?

The product rule for calculating momentum flux states that when two or more objects collide, the total momentum flux is equal to the sum of the individual momentum flux of each object. This can be expressed as F = mv, where F is the total momentum flux, m is the mass of the object, and v is the velocity.

## 3. How is momentum flux related to Newton's Third Law of Motion?

According to Newton's Third Law, for every action there is an equal and opposite reaction. This means that when two objects collide, they exert equal and opposite forces on each other, resulting in a transfer of momentum between the two objects. This transfer of momentum is known as momentum flux.

## 4. Why is momentum flux important in physics?

Momentum flux is important in physics because it helps us understand and predict the motion of objects in collisions or interactions. It also plays a crucial role in the conservation of momentum, which is a fundamental principle in physics.

## 5. How is momentum flux measured or calculated in experiments?

Momentum flux can be measured or calculated in experiments by using various instruments such as force sensors, accelerometers, and motion trackers. These instruments can measure the velocity and force of objects in motion, which can then be used to calculate the momentum flux using the product rule.

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