Clarification needed about accleration

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    Accleration
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Discussion Overview

The discussion revolves around the concept of acceleration in the context of a train moving at constant velocity and its impact on a person it collides with. Participants explore the implications of constant velocity and zero acceleration in a collision scenario, addressing questions of injury and motion dynamics.

Discussion Character

  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • One participant states that if a vehicle, like a train, is moving with constant velocity, then its acceleration is zero, leading to confusion about how a collision could cause injury.
  • Another participant argues that injury can occur due to deformation, suggesting that acceleration is not necessary for harm to happen.
  • A different viewpoint suggests that the person involved in the collision experiences acceleration as they are brought up to the speed of the train, which occurs rapidly during the impact.
  • One participant reiterates the initial question about the relationship between constant velocity and injury, emphasizing that while the train's acceleration is zero, the person's acceleration is significant during the collision.

Areas of Agreement / Disagreement

Participants express differing views on the relationship between constant velocity, acceleration, and injury in a collision. There is no consensus on the explanation of how injury occurs despite the train's zero acceleration.

Contextual Notes

Participants discuss the nuances of motion and acceleration, highlighting the complexity of the scenario without resolving the underlying assumptions about injury mechanics and the definitions of acceleration.

logearav
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revered members,
if velocity is constant acceleration is zero. now my question is if a vehicle moving with constant velocity, say a train, has constant velocity, so acceleration is zero. now if that train hits a person, why that person gets hurt, inspite of acceleration is zero? my son asked this question and i don't have answer to this? please help
 
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logearav said:
now if that train hits a person, why that person gets hurt, inspite of acceleration is zero?
Because the wheels of the train cut the person in 3 parts? You don't need acceleration to hurt someone, just deformation. And the acceleration of the person is not zero if he doesn't get overrun.
 
Last edited:
The poor person begins to move at the speed of the train and is accelerated to the velocity of the behemoth in something less than the time the train takes to pass the distance that the person's thickness represents within the train's path. Perhaps the time the body takes to be accelerated to its final velocity for a train moving at about 70km/h is on the order of 1/100 second.
Seconds can be marked rhythmically with a stick, the rate doubled to demonstrate 1/2 seconds, doubled again for 8ths, if you can tap 32 beats a second you're probably doing well.
I wonder if the child has seen the train far away and lacks visual comprehension of its speed.
 
logearav said:
if a vehicle moving with constant velocity, say a train, has constant velocity, so acceleration is zero. now if that train hits a person, why that person gets hurt, inspite of acceleration is zero?

In a collision with a person, the train's acceleration is (practically) zero. The person's acceleration is far from zero.
 

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