A box is at rest on the floor. The mass of the box is 150 kg and the coefficient of static friction between
the box and the floor is 0.30. The maximum force of
static friction is approximately

acceleration = (change in speed) / (time for the change)

change in speed = (20-120)= -100 m/s.

1.5 min = 90 sec

acceleration = -100/90 = -1.11 m/s^2.

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