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Name: Kristen
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Question:
Hello! My brother and I were watching a movie which prompted a discussion about the laws of motion. He argued that when a person jumps out of a vehicle, no matter which direction they jump in, they will continue to roll in the direction that the vehicle was going in. Now, I KNOW that with law of Inertia indicates that if an object is at rest INSIDE of an object in motion and THAT object were to be stopped but the object INSIDE was NOT stopped, that it would continue in motion in the same direction and speed that the outer object had been maintaining. HOWEVER, I argued with him that if you were to JUMP from the back of a moving vehicle (and tuck and roll), you would roll in the direction you jumped - BACKWARDS, because you have initiated your OWN path of motion. He said that I was wrong and that, under the same circumstances I just described, you would roll forward, towards the direction the vehicle was headed. If you could please let me know which one is correct and why I would appreciate it.



Replies:
The final velocity relative to the ground is v +/- u where v is the velocity of the vehicle and u is the velocity of the runner. Three possible answers: If positive, the person will move in the direction of the truck. If zero, the person will essentially go straight down. If negative, the final velocity will be in a direction opposite to the truck.

---Nathan A. Unterman



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