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Relative Velocity: Galillean Relativity
Name: Kristen
Status: other
Age: N/A
Location: N/A
Country: N/A
Date: N/A
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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Update: June 2012
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