Answer: 5grams
Step-by-step explanation:
Using the principle of moment to solve the question which states that the sum of clockwise moments is equal to the sum of anticlockwise moments
And moment = Force × Perpendicular distance from the direction of the force
*Check attachment for diagram
Taking moment about the pivot placed at C,
Sum of anticlockwise moments = (5×30) + (5×10)
Clockwise moment = M×40
Equating both and getting M
(5×30) + (5×10) = M×40
150+50 = 40M
200 = 40M
M = 5g
The single mass is 5grams.