Answer:
Step-by-step explanation:
Since the forces oppose each other (direction), the smaller is subtracted from the larger. The net force is
Fn = 100 - 40 = 60
Part B
Fn = m * a
a = 3.5 m/s^2
Fn = 60
60 = m * a
60 = m * 3.5 Divide by 3.5
60/3.5 = m
m = 17.143