The Inertia of two bodies, Relativity

[Roger Dynamic Motion]

Referring to the rider man who tosses a ball from a motorcycle ahead of him the equation is no accurate because the inertia of the body the (ball) is not taking in consideration

even if the ball has little inertia it should be included in the equation.

For example . let the man the rider be sitting on a small wagon and they together make 100 pounds and let the ball be 100 pounds so they both have the same inertia; now lets give a tiny push let say with a velocity 5 feet second to the wagon and tell the man to trow the ball ahead of him

should the reduced speed of the wagon , be consider in the equation ; no need to know the velocity of the ball in this case.

[KipIngram]

The equations work. I won't do it relativistically because it's so much more involved, but for your example classical techniques would say the following:

 

[ (wagon/man mass) + (ball mass) ] * (initial speed) = initial_momentum

 

"tiny push": (some_force * some_time) = added_momentum

 

(wagon/man mass) * (wagon final speed) + (ball mass) * (ball final speed) = final_momentum

 

Then you'd have initial_momentum + added_momentum = final_momentum

 

What about this is it that you think is wrong? You do need to know the ball's final speed in order to find the wagon's final speed, and all of the components of momentum are included.

[Roger Dynamic Motion]

The equations work. I won't do it relativistically because it's so much more involved, but for your example classical techniques would say the following:

 

[ (wagon/man mass) + (ball mass) ] * (initial speed) = initial_momentum

 

"tiny push": (some_force * some_time) = added_momentum

 

(wagon/man mass) * (wagon final speed) + (ball mass) * (ball final speed) = final_momentum

 

Then you'd have initial_momentum + added_momentum = final_momentum

 

What about this is it that you think is wrong? You do need to know the ball's final speed in order to find the wagon's final speed, and all of the components of momentum are included.

This is only an exercise to prove that the velocity of the man with the wagon must be deduced to the total velocity over all

[KipIngram]

Yes, the man/wagon velocity is altered by the things that happen too.