When the boxes are dragged, they move with the same speed and acceleration.
The combined drag on the boxes is 0.3(m + 4.65)*9.8 where 0.3 is the coefficient of kinetic friction and 9.8 is the acceleration due to gravity. (m+4.65)*9.8 is the total downward force, and the force due to friction is 0.3 of this.
To work out the horizontal forward force applied to...
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