Question

Figure represents a metre scale balancing on a knife edge at 20 cm mark. When a weight of 60 N is suspended from 10 cm mark. Calculate the weight of the ruler(in N).

• A. 30
• B. 60
• C. 15
• D. 20

Answer 1

The correct option is D 20

Weight of the ruler is acting from the centre of gravity of the ruler (i.e. the mid point 50 cm)
$w\times 30=60\times 10$
$w=\frac{60\times 10}{30}=20$