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Unformatted text preview: or Pcos18TWcos53=ma #3 girl Scale Assuming the girl accelerates downward and using the standard choice of coordinate system, this gives: TW g = m g (a) and T+NW bl = m bl (a) If the scale is to read zero, the normal force must be zero. So we have TW g = m g (a) and TW bl = m bl (a) If the block is to remain in contact with the scale, a for the block is zero. So we have TW g = m g (a) and TW bl = 0 or T=W bl Combining these two gives: W blW g = m g (a) or M bl (g) m g (g) = m g (a) or g ( M bl m g )/m g =a So g (7550)/(50) = a a = 0.5 g so a = 0.5 g The minus sign means that I chose the wrong direction for the acceleration in my initial assumption, so N S on Bl W Bl N T on S W S F Bl on S (N Bl on S ) T W g N S on B W Bl T a is 0.5 g UPWARD....
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 Spring '08
 Sperber

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