Question

e. A 200 cm meter rule is pivoted at the
middle point (at 50 cm point). If the weight
of 10 N is hanged from the 30 cm mark
and a weight of 20 N is hanged from its 60
cm mark, identify whether the meter rule
will remain balanced over its pivot or not.. ​

Answer 1

Solution:

According to the principle of moments, when an object is in rotational equilibrium, then

Total anticlockwise moments = Total clockwise moments

Total anticlockwise moments:

Length of lever arm = (50 – 30) = 20 cm

= 0.20 m

Since the length of the lever arm is the distance from its mid-point, where its balanced force

applied = 10 N

Anticlockwise moment = Lever arm x Force applied

= 0.20 x 10 = 2 Nm

Clockwise moment: Length of lever arm = (60 – 50)

= 10 cm

= 0.10 m.

Since the length of the lever arm is the distance from the mid-point, about which balanced Force

applied = 20 N

Clockwise moment = lever arm x force applied

                             = 0.10 × 20 = 2 Nm

Therefore,

Since the total anti-clockwise moment = total clockwise moment = 2 Nm, according to the  principle of moments, it is in rotational equilibrium ie, the meter rule remains balanced about its  pivot.