In the diagram shown, the blocks A, B and C weight, 3kg, 4kg and 5kg respectively. The coefficient of sliding friction between any two surface is 0.25. A is held at rest by a massless rigid rod fixed to the wall while B and C are connected by a light flexible cord passing around a frictionless pulley. Find the force F necessary to drag C along the horizontal surface to the left at constant speed. Assume that the arrangement shown in the diagram, B on C and A on B, is maintained all through. `(g=9.8m//s^2)`

Explanation

If 'C' moves with constant speed
`a_(c) = 0`
`F - T_(0) - f_(2)- f_(3) = 0`
`-f_(1) + T_(0) - f_(2) = 0`
`T = f_(1)`
`f_(1) = (3)/(4)g , f_(2) = (7)/(4) g , f_(3) = (15g)/(4)`
Solving ` " " F = 8` g N