Question

Figure shows a uniform metre rule placed on a fulcrum at its mid-point $O$ and having a weight $40gf$ at the $10cm$ mark and a weight of $20gf$ at the $90cm$ mark. Is the metre rule in equilibrium? If not, how will the rule turn?

• A. yes. The rule will not turn
• B. yes. The rule will turn anticlockwise
• C. No. The rule will turn anticlockwise
• D. No. The rule will turn clockwise

Answer 1

Answer: (C)

No. The rule will turn anticlockwise

Let us find individual moments of force.Considering 40 gf and 10 cm mark then 40 gf is at a distance of 40 cm from point O. we get moment of force is equal to $40\ast 40=1600gfcm.$
Now let us consider 20 gf and 90 cm mark then 20 gf is at a distance of 40 cm to the right to O. We get moment of force as $20\ast 40=800gfcm$. Both are not equal hence not in equilibrium.As 1600 gf cm is in anticlockwise in direction it turns in that anti clockwise direction.