The image of the uniform beam is missing, so i have attached it.
Answer:
Option D: 90N acting downwards, 20cm to the left of the midpoint
Explanation:
Taking moments about the pivot, for the beam to be balanced, the moments to the left of the pivot must be equal to the moments to the right of the pivot.
Thus, it also means that; anti clockwise moment = clockwise moment.
Now, from the image, the moment of the left force about the pivot is an anti clockwise moment = 60 × 30 = 1800 N.cm
Now, for the beam to be rebalanced, we need a clockwise moment to the right of the pivot that is equal to 1800 N.cm.
Thus, the clockwise moment would have to be gotten from a downward force to the right of the pivot.
From the options given, the only downward force to the right of the pivot that produces a moment equal to 1800 N.cm is;
Option D: 90N acting downwards, 20cm to the left of the midpoint
