Sophia pushes with a 40-N horizontal force on a 4.0-kg box resting on a lab bench. The box slides against a horizontal friction force of 24 N. show that the box acceleration at 4.0 m/s2

   a = 4.0 m / s²,     so the result of the exercise is correct

Explanation:

This is an exercise on Newton's Second Law

               F = m a

we create a reference system with the horizontal x axis and the vertical y axis

Axis y

             N -W = 0

X axis

              F -fr = m a

give us the applied force F = 40 N, the value of the friction outside fr = 24 N

               a = (F - fr) / m

let's calculate

              a = (40 - 24) / 4

              a = 4.0 m / s²

so the result of the exercise is correct

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