Does Static Friction Contribute to Work in an Inclined Car?

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Homework Help Overview

The discussion revolves around the work done on a car moving down an incline, specifically questioning the role of static friction in this context. Participants are examining the forces acting on the car, including the normal force and static friction, while considering the implications of these forces on work done.

Discussion Character

  • Exploratory, Assumption checking

Approaches and Questions Raised

  • Participants are attempting to understand why static friction is considered in the context of work done, despite the displacement of both the normal force and static friction being zero. There is also discussion about the definition of work and whether static friction contributes to it.

Discussion Status

Some participants have provided insights regarding the calculation of work, suggesting that the expected approach may involve the displacement of the center of mass rather than the point of contact. There appears to be a divergence in understanding the application of work in this scenario, with no clear consensus reached.

Contextual Notes

Participants are navigating the nuances of work and force interactions, particularly in the context of static friction and its implications for the problem at hand. There is mention of a potential misunderstanding regarding the definition of work in relation to the forces acting on the car.

Zhalfirin88
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Homework Statement


A car is going down an incline with a constant acceleration.
How much work was done on the car by the force of the road going down the hill? (neglect energy losses due to air resistance, rolling friction, etc.)

The Attempt at a Solution


There are 2 forces acting on the car from the road, the normal force and static friction. But the displacement of both the normal force and static friction are both 0, so how is static friction doing work?
 
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Zhalfirin88 said:
There are 2 forces acting on the car from the road, the normal force and static friction. But the displacement of both the normal force and static friction are both 0, so how is static friction doing work?
Technically, the static friction does no work on the car.
 
That's exactly what I put, 0, and it was marked wrong. I'm trying to figure out why it was marked wrong
 
Work done, ΔW= F.Δx
Because Ff opposes the motion, it is directed opposite to x

the work done on the car by friction,
W=-Ff.x
 
Last edited:
Zhalfirin88 said:
That's exactly what I put, 0, and it was marked wrong. I'm trying to figure out why it was marked wrong
They probably wanted you to calculate F*Δx, where Δx is the displacement of the center of mass, not the point of contact. Strictly speaking, that's not work, but pseudowork.
 

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