Determining the weight of an object, given force to move it

[Bearbull24.5]

Homework Statement

This is the second part of a problem. In the first problem I determined friction coefficient of an 8N block requiring 2.9 N of force to move is .3625.

The second part of this problem asks: If a weight is added to the block and it now requires 5.7 N to move both at a constant acceleration, what would the weight of the block be?

Homework Equations

w=mg
f=uN
u=f/N

The Attempt at a Solution

I attempted to use the friction coefficient I found in the first problem and set it up as N=f/u. This provided me with the wrong answer.

 

[Doc Al]

I attempted to use the friction coefficient I found in the first problem and set it up as N=f/u. This provided me with the wrong answer.

That method should work just fine, assuming you understand how N relates to the answer they want. Are they asking you to provide the amount of weight added to the block?

 

[Bearbull24.5]

That method should work just fine, assuming you understand how N relates to the answer they want. Are they asking you to provide the amount of weight added to the block?

The way the question is set up I believe they want the total weight

 

[Doc Al]

The way the question is set up I believe they want the total weight

To get the total weight of the block plus whatever was added, the method you showed would be correct.

The wording of the question seemed a bit ambiguous to me--they could also have been asking for the weight added to the block.