Question 6(i)
Shyam is trying to balance a meter rod on his finger as shown in the diagram. Two weight 50 gf and 200 gf at 40 cm and 95 cm respectively and his finger at 70 cm.
Find the anti-clock wise moment and clockwise moment.
(b) Find the weight of meter rod.
(a) Let W be the weight of the rod.
For uniform meter rod, its weight acts at 50 cm.
Clockwise moments = [200 x (95-70)] = 200 x 25 = 5000 Nm
Anticlockwise moments = [50 x (70 - 40)] + [W x (70 - 50)]
= [50 x 30] + [W x 20]
= 1500 + 20W
(b) According to principle of moment :
Anticlockwise moment = Clockwise moment
1500 + 20W = 5000
W = = 175 N
Hence, weight of meter rod = 175 N
As W = 175 N, hence, anticlockwise moment = 1500 + 20W = 1500 + (20 x 175) = 1500 + 3500 = 5000
Hence, anticlockwise moment = 5000 Nm