A powered toy car moving at a constant speed

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Discussion Overview

The discussion revolves around the dynamics of a powered toy car moving at a constant speed of 1 m/s. Participants explore concepts related to forces acting on the car, particularly focusing on friction, traction, and the implications of deceleration when power is removed. The scope includes theoretical reasoning and conceptual clarification regarding free body diagrams (FBD).

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • One participant asserts that when the car is moving at a constant speed, there is no net force acting on it, raising questions about the presence of friction and traction.
  • Another participant suggests that the determination of whether air resistance is negligible depends on the desired accuracy and introduces the idea of other retarding influences, such as vibrations.
  • A participant questions what evidence could demonstrate the existence or absence of traction, proposing hypothetical scenarios involving a frictionless surface and a movable road.
  • One participant emphasizes that the discussion about free body diagrams does not require experimental validation, suggesting a focus on theoretical aspects instead.

Areas of Agreement / Disagreement

Participants express differing views on the role of traction and friction in the context of the toy car's motion. There is no consensus on whether traction exists while the car is moving at a constant speed, and the discussion remains unresolved regarding the implications of deceleration when power is removed.

Contextual Notes

Participants highlight the complexity of defining forces acting on the car, including the potential influence of various retarding forces and the conditions under which traction may or may not be present.

Who May Find This Useful

This discussion may be of interest to individuals exploring concepts in physics related to forces, motion, and the analysis of free body diagrams, particularly in educational or theoretical contexts.

superdave
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Okay, so please help settle a dispute.

A toy car is moving at a constant speed of 1 m/s. The car is powered by a battery.

Now, when the car is going at a constant speed, there is obviously no net force on the car.

The dispute comes when trying to draw a FBD.

Is there friction (traction) between the ground and the wheels?

If so, what force is balancing out the traction to keep the car from accelerating? At that speed, air resistance is negligible, correct?

If not, then why will the car only move when powered on? As soon as power stops, the car decelerates which indicates where was a negative force on the car being countered by traction.
 
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Whether air resistance is negligible or not depends on how accurate you want to be. What other retarding influences can you think of? For instance, does the car vibrate at all as it rolls across the ground? Where does the corresponding energy come from?

Edit: Additionally, the fact that the car decelerates when you remove power does not demonstrate that there was forward traction while the car was moving. It could, alternately, demonstrate that there is retarding traction while the car is slowing down.
 
So if I were to take this toy car and
jbriggs444 said:
Whether air resistance is negligible or not depends on how accurate you want to be. What other retarding influences can you think of? For instance, does the car vibrate at all as it rolls across the ground? Where does the corresponding energy come from?

Edit: Additionally, the fact that the car decelerates when you remove power does not demonstrate that there was forward traction while the car was moving. It could, alternately, demonstrate that there is retarding traction while the car is slowing down.
What would demonstrate the lack of or existence of traction?

If the car were to roll at a constant speed onto a near frictionless surface in a vacuum, moving normal to the interface, if there was no traction then it should keep rolling at the same speed on this new surface?

Or, if the car were to roll at a constant speed onto a road that is free to move, if there was traction, then the road would move backwards as the car moved forward? If there was no traction while moving at a constant speed, the car should just keep moving as normal.
 
I thought the dispute was about a free body diagram. You do not have to run an experiment to draw a free body diagram.
 

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