How Much Force is Needed to Move a 50kg Crate?

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Homework Help Overview

The problem involves calculating the force required to move a 50kg crate resting on the floor, given a coefficient of static friction of 0.5. Participants are exploring the relationship between frictional force and normal force in the context of static friction.

Discussion Character

  • Conceptual clarification, Mathematical reasoning, Problem interpretation

Approaches and Questions Raised

  • Participants discuss the equation for frictional force, F = uR, and the need to determine the normal reaction force. There is uncertainty about how to apply the equation and what values to use for calculations.

Discussion Status

The discussion is progressing with participants attempting to calculate the normal force and frictional force. Some guidance has been provided regarding the use of the equation and the relationship between mass, weight, and friction. Multiple interpretations of the problem are being explored, particularly regarding the calculations involved.

Contextual Notes

Participants are working under the constraints of a homework assignment, which may limit the information they can reference or the methods they can use. There is ongoing questioning about the correct application of the equations involved.

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Homework Statement



A 50kg crate rests on the floor. The coefficient of static friction is .5. The force parallel to the floor needed to move the crates is most nearly:

Choices:
50N
125N
250N
500N

Homework Equations


I have no idea what equation to use for this equation.



The Attempt at a Solution



No attempts yet since I don't know which equation to use.
 
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Do you know the equation that F=uR, where F is the frictional force and R is the normal reaction?
 
rock.freak667 said:
Do you know the equation that F=uR, where F is the frictional force and R is the normal reaction?

I have seen it before but my teacher never really used it. But I would like to learn how to use it. Can you show me?
 
Firstly, you'll need to find the normal reaction,R. In this case it is simply the crate's weight. When you have that, put that into F=uR where u is the coefficient of friction. Then compare the value of friction that you get to the answers given.
 
rock.freak667 said:
Firstly, you'll need to find the normal reaction,R. In this case it is simply the crate's weight. When you have that, put that into F=uR where u is the coefficient of friction. Then compare the value of friction that you get to the answers given.

Ok. That sounds pretty easy. So for that it would look like this..

F= uR
F= (.5)(50)
I guess I multiply right? And that gives me 25N but that isn't an answer.

Did I do something wrong?
 
vballkatie22 said:
Ok. That sounds pretty easy. So for that it would look like this..

F= uR
F= (.5)(50)
I guess I multiply right? And that gives me 25N but that isn't an answer.

Did I do something wrong?

50kg is the crate's mass. To find its weight you need to multiply the mass and the acceleration due to gravity
 
rock.freak667 said:
50kg is the crate's mass. To find its weight you need to multiply the mass and the acceleration due to gravity

Ok. So to find the weight I take 50kg and times that by acceleration which is 9.8 (gravity)
To get 490.

Correct?
 
vballkatie22 said:
Ok. So to find the weight I take 50kg and times that by acceleration which is 9.8 (gravity)
To get 490.

Correct?

yes that is the weight of the crate and hence its normal reaction. Now what is the frictional force (this also is the frictional force which causes the crate to be in limiting equilibrium)
 
rock.freak667 said:
yes that is the weight of the crate and hence its normal reaction. Now what is the frictional force (this also is the frictional force which causes the crate to be in limiting equilibrium)

Would it be .5? I don't really know.
 
  • #10
vballkatie22 said:
Would it be .5? I don't really know.

Try F=uR => F=(0.5)(490)
 
  • #11
Ok.. so the answer would be 245N but the closest one I have is 250N.

Thanks!
 

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