Can rapid acceleration have momentum?

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  • Thread starter Thread starter BillyJohnson1992
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    Acceleration Momentum
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Discussion Overview

The discussion revolves around the concept of momentum in the context of a top fuel dragster's acceleration and deceleration. Participants explore how momentum behaves when the dragster's engine is cut off during different scenarios of motion, specifically focusing on the implications of rapid acceleration and the effects of external forces.

Discussion Character

  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • Some participants assert that when the engine cuts fuel delivery, the dragster will slow down immediately due to the lack of force exerted by the engine.
  • Others argue that momentum is defined as velocity times mass, and an object retains its momentum as long as no net external force acts on it.
  • A participant emphasizes that the period of acceleration does not alter the physics of deceleration, suggesting that velocities decrease at the same rate if all other factors remain constant.
  • There is a clarification that momentum remains unchanged until a net external force is applied, which may include frictional forces acting on the dragster.

Areas of Agreement / Disagreement

Participants express differing views on how momentum is affected when the dragster's engine is cut off, indicating that multiple competing views remain without a clear consensus on the implications of rapid acceleration on momentum.

Contextual Notes

The discussion highlights the importance of considering external forces, such as friction, and the conditions under which momentum is maintained or altered. There are unresolved aspects regarding the specific conditions that might affect the dragster's deceleration.

BillyJohnson1992
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A top fuel dragster can accelerate from 0 to 300mph in 4 seconds.

Scenario 1: Top fuel dragster is driving at a constant speed of 300mph. Driver cuts the fuel delivery to the engine. The speed will immediately decrease.

Scenario 2: Top fuel dragster is accelerating violently, at the 1 second mark the speed is already 100mph and going up at a dramatic pace. Driver cuts the fuel delivery to the engine. Will the speed immediately decrease?

Help! :confused:
 
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Yes, it will slow down at the moment the engine does not deliver force on the wheels anymore, and if it gets no fuel the engine cannot exert any force.

Momentum is velocity times mass. An object will keep the same momentum as long as no force is acting on it. There are different kinds of friction forces acting on the dragster and when it is speeding up (and its momentum is increasing) the force between the wheels and the ground is larger than the friction forces (air friction, friction in parts of engine and bearings). Those friction forces will slow the dragster down when there is no forward force.
 
Scenario 1: Top fuel dragster is driving at a constant speed of 300mph. Driver cuts the fuel delivery to the engine. The speed will immediately decrease.

Scenario 2: Top fuel dragster is accelerating violently, at the 1 second mark the speed is already 100mph and going up at a dramatic pace. Driver cuts the fuel delivery to the engine. Will the speed immediately decrease?

The fact that the dragster in Scenario 2 had a period of acceleration before it's period of deceleration doesn't change the physics of the situation. The velocities decrease at the same rate if all other factors are held constant.
 
An object will keep the same momentum as long as no force is acting on it.

... as long as no net external force is acting on it.
 

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