EK Physics 1001 #453 Torque

[tshank]

Hi, I have a question on this problem. My equation gives me (12)(10)(.25) = F(.75). Solve for x. Is this wrong? I don't see how they get 40 N as the minimum.

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[Cawolf]

T(net) = 0 = F(0.75) - (mg)(0.25)

0.75F = 0.25m

F = (0.25m)/0.75 = mg/3 = (12)(10)/3 = 120/3 = 40N

I typed all this and then looked at your equation to see that F solves for 40 also . . . so you have it right?

 

[tshank]

Yeah, that makes sense, I just messed up dividing 30/.75 Any tricks on how to divide decimals??? I like your wave of solving it, but I have a hard time moving symbols first.

 

[techfan]

30/.75=30*4/3=10*4?

 

[Cawolf]

Yeah, that makes sense, I just messed up dividing 30/.75 Any tricks on how to divide decimals??? I like your wave of solving it, but I have a hard time moving symbols first.

The way I approach that math is this...we want to know what (12)(10)(0.25)/(0.75) is.

F = (12)(10)(0.25)/(0.75) = (12 * 10)(0.25/0.75) here it is easier to see that 0.25/0.75 = 1/3

=(120)(1/3) = 120/3 = 40

 

[tshank]

Right on. Thanks!