Finding out applied force in order to get acceleration

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Homework Help Overview

The problem involves a box being pushed across a horizontal surface with an initial velocity, and participants are tasked with determining how far the box slides before coming to rest. The context includes concepts from dynamics and friction, specifically focusing on applied forces and kinetic friction.

Discussion Character

  • Exploratory, Assumption checking, Problem interpretation

Approaches and Questions Raised

  • Participants discuss the relationship between applied force, friction, and acceleration. There are attempts to calculate the normal force and frictional force, but uncertainty arises regarding the necessity of an applied force. Some participants suggest using conservation of energy as an alternative approach.

Discussion Status

The discussion is ongoing, with participants exploring different interpretations of the problem. There is acknowledgment of the complexity surrounding the applied force, and some guidance has been offered regarding alternative methods to approach the problem.

Contextual Notes

There is a noted ambiguity about the presence of an applied force, with some participants suggesting that it may not be necessary, while others assert that an applied force is indeed present based on external checks. This uncertainty influences the direction of the discussion.

DPXJube
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Homework Statement


A person pushes a box across a horizontal floor with an initial velocity of 5.2m/s. The box has a mass of 22kg, and the coefficient of Kinetic friction between the box and the floor is 0.44. How far does the box slide before coming to rest?


Homework Equations


μk = FK/FN
Fnetx = FA - FK(assuming that right is positive and left is negative)
V2 - V1 = 2aΔd


The Attempt at a Solution


Rearrange μk = FK/FN to FK = μkFN
Find Normal Force
FN = FG
FG = mg
Get 215.6 for FG which is in turn the normal force.
FK = (0.44)(215.6)
FK = 94.9
Find acceleration
Fnet = FA - FK
ma = FA - FK

And at this point I do not know what to do as I do not have the apllied force.
The plan after that was to rearrange the Kinematic equation into Δd = V2-V1/2a and fill in for that.
Unless of course my Free Body Diagram is wrong and there IS no applied force, although that seems unlikely.
 
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Based on my reading of this problem it seems that the correct answer is the one that you hit on at the end, that there is no applied force in this problem.
 
DPXJube said:

Homework Statement


A person pushes a box across a horizontal floor with an initial velocity of 5.2m/s. The box has a mass of 22kg, and the coefficient of Kinetic friction between the box and the floor is 0.44. How far does the box slide before coming to rest?


Homework Equations


μk = FK/FN
Fnetx = FA - FK(assuming that right is positive and left is negative)
V2 - V1 = 2aΔd


The Attempt at a Solution


Rearrange μk = FK/FN to FK = μkFN
Find Normal Force
FN = FG
FG = mg
Get 215.6 for FG which is in turn the normal force.
FK = (0.44)(215.6)
FK = 94.9
Find acceleration
Fnet = FA - FK
ma = FA - FK

And at this point I do not know what to do as I do not have the apllied force.
The plan after that was to rearrange the Kinematic equation into Δd = V2-V1/2a and fill in for that.
Unless of course my Free Body Diagram is wrong and there IS no applied force, although that seems unlikely.

Hi DPXJube,

How about we try conservation of energy since your usual method is not working :wink:

The change in kinetic energy = work done by the frictional force.
 
ActionFrank said:
Based on my reading of this problem it seems that the correct answer is the one that you hit on at the end, that there is no applied force in this problem.
Unfortunately I've checked the answer for the question and there is indeed an applied force.
 
DPXJube said:
Unfortunately I've checked the answer for the question and there is indeed an applied force.

In that case, your question cannot be solved. What was the answer given?
 

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