Question
A7 mbar is pivoted at 2 m from the left end.Aforce of 60 N is applied downwardly on the left end and a force of 20 N is applied downwardly on the right end. What would be the clockwise and counter -clockwise moments and in which direction would the bar rotate? (a) 80 Nm counter -clockwise, 100 Nm clockwise counter-clockwise rotation (b) 60 Nm counter -clockwise, 100 Nm clockwise clockwise rotation (c) 120 Nm counter -clockwise, 100 Nm clockwise counter-clockwise rotation (d) 120 Nm counter-clockwise 100 Nm clockwise, clockwise rotation
Solution
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(256 Votes)
Ferdinand
Elite ยท Tutor for 8 years
Answer
Here's how to solve this problem and determine the rotation:**1. Calculate the Counter-Clockwise Moment:*** The 60 N force on the left end creates a counter-clockwise moment.* Moment = Force x Distance from pivot* Counter-clockwise moment = 60 N * 2 m = 120 Nm**2. Calculate the Clockwise Moment:*** The 20 N force on the right end creates a clockwise moment.* We need to find the distance of this force from the pivot. Since the bar is 7 m long and the pivot is 2 m from the left end, the right end is 7 m - 2 m = 5 m from the pivot.* Clockwise moment = 20 N * 5 m = 100 Nm**3. Determine the Net Moment and Rotation:*** The counter-clockwise moment is 120 Nm, and the clockwise moment is 100 Nm.* Since the counter-clockwise moment is greater, the bar will rotate counter-clockwise.* Net moment = 120 Nm (counter-clockwise) - 100 Nm (clockwise) = 20 Nm counter-clockwise**Therefore, the correct answer is (c) 120 Nm counter-clockwise, 100 Nm clockwise, counter-clockwise rotation.**