Figure (5-E8) shows a uniform rod of length 30 cm having a mass of 3.0 kg. The strings shown in the figure are pulled by constant forces of 20 N and 32 N. Find the force exerted by the 20 cm part of the rod on the 10 cm part. All the surfaces are smooth and the strings and the pulleys are light.
Resultant force = 32 - 20 = 12 N
Acceleration of the block = 
= 
= 4 m/s2 (towards right)
m1= 3 kg × (
) = 1 kg
m2 = 3 kg × (
) = 2 kg
Force exerted by m1 on m2 = m1a = 1*4 = 4 N = Force exerted by m2 on m
Therefore, total force = 20 + 4 = 24 N
2