- #1

HazyMan

- 51

- 3

- Homework Statement
- A box of mass M rests on a flat surface. A bullet of mass m and velocity u moves in a straight line and collides with the box and it gets stuck in it, FORMING ONE NEW BODY. What's the force that the bullet applies to the box?

- Relevant Equations
- F=Δp/Δt

I tried out the [tex]F=Δp/Δt[/tex] equation and i came up with a change of momentum of the box-bullet fusion [tex](M+m)V-0[/tex], but the textbook says otherwise (using a change of momentum of JUST the box itself, excluding the bullet). According to the textbook, the correct change is [tex]MV-0[/tex], without the added mass of the bullet being in the expression. Which of the two is really correct and why? I am supposing that the momentum the box gains is the momentum it gains considering the fact that it's fused with the bullet, while the book seems to ignore that the bullet is stuck in the box, and acts as if the box's gained momentum is JUST ITS OWN MASS times its velocity. I could really use a hand in this situation, thanks for reading!

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