(a) Three of the quantities are in principle straightforward to measure (using,
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Question
(a) Three of the quantities are in principle straightforward to measure (using, say, a spring scale): F, WA, and WB. The other four, fT, f, NT, and N, are "invisible"—that is, a little bit harder to measure directly. (Though you might be able to think of a way!) If you knew the three easily measurable quantities, could you find the other four (invisible) ones? If so, write equations to express each invisible one in terms of the three measurable ones. (Enter NONE for any variable that can not be expressed this way.)
fT=
f=
NT=
N=
(b) If a variable can not be represented solely in terms of F, WA, and WB, explain what else you would need. (If all equations can be represented in this way, state so below.)
A heavy block, labeled "A", is sitting on a table. On top of that block is a lighter block, labeled "B" as shown in the figure below. In this problem, we will be looking at the relationships between the various forces in the problem under various circumstances. In order to simplify the equations we write, we will not use our full "who is acting on whom" force notation, but wil use the following simplifications. (Note that we have taken for granted that you understood and could use Newton's 3rd law.) NF AF (force of the finger pushing block A) ·NA-, B-NB-A-N (the normal forces acting between the blocks) ·NT-A-Ny (the normal force of the table acting on block A) fT+A-(the friction force between block A and the table) FA B B -A f (the friction force between the two blocks) WEWa (weight of block A) ·WE B = WB (weight of block B) we then have the seven symbols representing all the forces in the problem: F, NT, N, fT, f, WA, and WBExplanation / Answer
ft=frictional force between table and block A=u(WA+W b)) here u=coefficient of friction between A and table surface
f=frictional force between blocks =u(mue)1WB
NT=WA+WB
N=WB
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