The magnitude of the frictional force of the box is 65 N
From the question given above, the following data were obtained:
The frictional force acting on the box can be obtained as follow:
Fₙ = Fₐ – Fբ
70 = 135 – Fբ
Collect like terms
70 – 135 = – Fբ
–65 = –Fբ
Multiply through by –1
Thus, the frictional force of the box is 65 N
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