Centre of mass and translational motion

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Homework Help Overview

The problem involves a flatcar in motion with a worker walking on it, focusing on the concepts of center of mass and translational motion. The scenario includes a flatcar with a specified mass and length, moving at a constant speed, while a worker moves in the direction of the car's motion.

Discussion Character

  • Exploratory, Assumption checking, Problem interpretation

Approaches and Questions Raised

  • Participants discuss the calculation of the center of mass speed and question the correctness of the derived value. There is uncertainty about how to determine the distance traveled by the car and the implications of the worker's movement on the system's overall speed.

Discussion Status

Some participants are exploring the relationship between the speeds of the car and the worker, while others are questioning the assumptions made regarding the initial conditions. Hints have been provided to guide the exploration of the problem without reaching a definitive conclusion.

Contextual Notes

Participants are navigating the constraints of the problem, including the need to consider the reference frames of the car and the worker, as well as the implications of the conservation of momentum in a frictionless environment.

godwinscareer
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Homework Statement



A 270 kg flatcar 20 m long is moving with a speed of 5.0 m/s along horizontal frictionless rails. A 90 kg worker starts walking from one end of the car to the other in the direction of motion, with speed 3.0 m/s with respect to the car.

Homework Equations



MVcm = m1v1 + m2v2

The Attempt at a Solution



I found the Vcm to be 4.5 m/s

I have no idea how to find the distance traveled by the car...can someone please help me
 
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godwinscareer said:
I found the Vcm to be 4.5 m/s
How did you come up with that? (Hint: You are told that the initial speed of everything is 5.0 m/s.)
 
I used the equation to find that...i don't know if its right or wrong..i don't know how to approach the problem
 
The speed of the center of mass is given as 5.0 m/s. Since Vcm can't change, use that equation to figure out the speed of the car while the man is walking. Hint: If the speed of the car with respect to the ground is called +V, and the speed of the man with respect to the car is -3 m/s, what would be the speed of the man with respect to the ground in terms of V?
 

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