How Strong is the Force Between Two Positive Charges?

AI Thread Summary
The discussion revolves around calculating the force between two positive charges using the formula F=Ke(Q1*Q2)/d^2. A user attempts to solve the problem by converting the charges from microcoulombs and millicoulombs to coulombs and the distance to meters, initially arriving at a force of 0.2088. After receiving feedback about potential errors in the order of magnitude, the user recalculates and arrives at 2.088 but still receives an incorrect answer. Confusion arises regarding significant figures and the accuracy of the conversion for the charge values. The user expresses frustration over the repeated mistakes and seeks clarification on the calculations.
corey7
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Homework Statement


What is the magnitude of the force a +15 µC charge exerts on a +2.6 mC charge 41 cm away?


Homework Equations


F=Ke(Q1*Q2)/d^2


The Attempt at a Solution


Well I plugged in the numbers for the variables. Converted 15 and 2.6 to coulombs and 41 to meters. I did the math and got like .2088. I have to input my answer on this site and I have five tries to do so. I used three already so I really don't want to screw up again without help...or something like that...you get what I'm saying.
 
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Welcome to PF.

I think your orders of magnitude are off. Check your powers of 10.
 
Well you uhh may be right, and thanks for the welcome. I tried it again and I got 2.088 but I put that in and still got it wrong. Me == confused now. Maybe it wants an exact answer or its screwing me over for sig figs or something...maybe I'm just wrong.
 
Ooof I read it over...hehe...yeah I converted 2.6 as if it were micro
 

Thread 'Errors and significant figures'

I multiplied the values first without the error limit. Got 19.38. rounded it off to 2 significant figures since the given data has 2 significant figures. So = 19. For error I used the above formula. It comes out about 1.48. Now my question is. Should I write the answer as 19±1.5 (rounding 1.48 to 2 significant figures) OR should I write it as 19±1. So in short, should the error have same number of significant figures as the mean value or should it have the same number of decimal places as...
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Thread 'A cylinder connected to a hanging mass'

Thread 'A cylinder connected to a hanging mass'

Let's declare that for the cylinder, mass = M = 10 kg Radius = R = 4 m For the wall and the floor, Friction coeff = ##\mu## = 0.5 For the hanging mass, mass = m = 11 kg First, we divide the force according to their respective plane (x and y thing, correct me if I'm wrong) and according to which, cylinder or the hanging mass, they're working on. Force on the hanging mass $$mg - T = ma$$ Force(Cylinder) on y $$N_f + f_w - Mg = 0$$ Force(Cylinder) on x $$T + f_f - N_w = Ma$$ There's also...
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