previous 1 12of13next Moment of a Couple Part A As shown, a submarine hatch door
ID: 1658102 • Letter: P
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previous 1 12of13next Moment of a Couple Part A As shown, a submarine hatch door is to be opened by appliying two oppositely oriented forces of equal magnitude F 70.0lb at points A and B on the hatch door wheel. The radi of the wheets inner and outer rings are 1.90 ft and T20.700ft, respectively. (Figure 1) Calculate the moments MA and Mn about point D for the forces applied at points A and B. Then, determine the resulting couple moment MR Assume that a positve moment produces a counterdlockwise rotation whereas a negative moment produces a clockwise rotation Learning Goal: To be able to calculate couple moments A couple is defined as two parallel forces, separated by a distance, that have equal directions. A couple only produces a rotation in a specified direction. The moment produced by a couple is called a couple moment Express your answers numerically in pound-fet to three significant figures separated by commas. Hints vec MM, Me 0.81.181.1 lb noure 1) of SubmitMy Answers Give Up Incorrect; Try Again; 3 attempts remaining: no points deducted Term 2 Not quite. Check through your calculations; you may have made a rounding error o used the wrong number of significant figures. 12 Part B This question will be shown after you complete previous question(s) Part CExplanation / Answer
Given F = 70 lb
outer ring radius r1 = 1.9 ft
outer ring radius r2 = 0.7 ft
so moment about point D on the rim of the inner circle is
Ma = -F*(r1 + r2) = -70*(1.9 + 0.7) = -182 lbs ft ( clockwise moment means -ve sign)
Mb = -F(r1 - r2) = -70*(1.9 - 0.7) =-84 lbs ft
total moment = Ma + Mb = -266 lbs ft
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