Newton's second law of motion states that the resultant force is directly proportional to the rate of change in momentum. This gives us the formula,
The resultant force (F)= Ma, where m is the mass, and a is the acceleration.
Therefore;
F = 12 (3)
= 36 N
Albert applied a force of 49 N to the box but due to friction force only 36 N of the force made the object to move.
Thus the net force was 36 N