Two blocks of masses m1=4 kg and m2=6 kg are connected by a string of negligible mass passing over a frictionless pulley as shown in the figure. The coefficient of friction between block m1 and the horizontal surface is 0.4. When the system is released, the masses m1 and m2 start accelerating. What additional mass m should be placed over mass m1 so that the masses (m1+m) slide with a uniform speed?
11 kg
For the system to move with a uniform speed, net force on each block should be zero.
T=m2g
Also, T=f=μ(m1+m)g⇒m2g=μ(m1+m)g⇒m2=μ(m1+m)⇒6=0.4(4+m)⇒m=11 kg
Hence, the correct choice is (c).